Shadal himself admits to this in a letter to Shlomo Yehuda Rapaport published in Igrot Shadal Volume II p.246:
ואני גם כי אינני מאוהביו כבר קיבלתי פירושו (נגד ההלכה) בפסוק לא תקיפו פאת ראשכם שאינו אלא על מת וקִבלתיו לעצמי למעשה אע"פ שאין אני מורה כן לאחרים כי אין לי עסק בהוראה
As for me, though I am not one of [Ibn Ezra's] friends, I have already ...
This is a can of such powder (cream) that Jews would use on the Lower East Side around 100 years ago. If you look closely you will see that it says Mutar based off the teshuva of the Noda B'Yehuda, YD 81.
Yiddish text on top says: א שייוו אהן א רייזאר נור מיט א פוידער איז מותר.
It is permitted to use depilatory cream (but not on Shabbat).
R Jack Abramowitz writes
The Torah only prohibits using a razor to cut the corners of the
beard. There are five such corners and many positions when it comes to
the details, so a pious person should not use a razor on any part of
his beard, nor even on his mustache or on his neck. There ...
As the Rambam states in H. A"Z 12:8:
ואינו חייב עד שיגלחנו בתער--שנאמר "ולא תשחית, את פאת זקנך" (ויקרא יט,כז), גילוח שיש בו השחתה; לפיכך אם גילח זקנו במספריים, פטור. ואין המתגלח לוקה, עד שיסייע.
One is liable only when one shaves with a razor, as [implied by Leviticus 19:27]: "Do not destroy the corners of your beard." [We can infer that this applies ...
Rav Herschel Schachter told me that the reason they do it is because they are afraid that a hair will be left out of the mikveh when they do tevila. To avoid this problem they shave their heads. I have also heard that they suspect that there will be tangles, which are חציצה for the tevila, so they shave their heads. Neither of these reasons would really ...
These are vey good questions and I do not have all the answers, but one thing I wish to clarify as this misconception is quite widespread: this custom was not invented by Hassidim. In fact, this custom predates chassidus and possibly dates back to the days of the rishonim. See for example Shut tashbatz part 3, 299, where he mentions a custom of קציצת הפיאות ...
A written (albeit 2nd hand) source for R. Moshe is in the Sefer Meged Giv'os Olam of his longtime student R. Michel Shurkin. He discusses the view of R. Moshe at length in chelek one starting on page 94, and is in turn quoted by R. Ovadiah in Yabia Omer (vol. 9 YD ch. 10 #18) R. Moshe remarked (as quoted there) that he didn't include this in Igros Moshe ...
Pischei Tshuva in Yoreh Deah 181 #5 brings opinions that it is allowed, warning however, not to scrape the application off with a knife.
אבל במשיחה הנעשה כעין טיח טיט והחריפות שבו שורף השער מותר דזה הוי השחתה בלי גלוח. אך אם אחר המשיחה נשאר טיח זה על פניהם אין נגררו בסכין אלא ביד ע"ש וע' בזה בתשובת שמש צדקה חלק י"ד סי' ס"א בד"ה לבד זה:
In the course of my translating Shadal’s perush on Vayikra, I have given a good deal of thought to this difficult issue. Here are some of my conclusions:
Before criticizing Shadal, it is important to scrutinize the actual words of his letter to Rapoport. Nowhere does he say that he shaves with a razor; nowhere does he admit to violating the normative ...
The following picture, from this page which has since gone down, depicts all the opinions with pictures as to where exactly those five points are.
Translation of the Hebrew text:
Shulchan Aruch (Yoreh Deah), siman 181:11: The corners of the beard are five, and there are a multitude of opinions (as to what they are). Therefore one who fears heaven should ...
Borrowing from this answer, which quoted from this site (and setting aside the discussion of electric razors, because they are not the topic at hand):
Rav Moshe Feinstein understood the aforementioned sugyah in accordance with this latter approach. According to this approach, when the Gemara rules that an item which both destroys and shaves is prohibited, ...
Nitei Gavriel Aveilus2 3:1 says that the prohibition of cutting hair beyond 30 days is only for a parent, which requires one to be told that he looks unkempt prior to taking a haircut. For one who is mourning a child or sibling the prohibition is only for 30 days and then may cut his hair immediately after the 30 days whenever he wants because the Aveilus ...
The same logic used with an electric shaver would apply here. If it's not "razor-sharp", it's fine.
There are a few different definitions; Rabbi Heinemann of the Star-K, shlit'a, in the name of R' Moshe Feinstein suggests taking a whisker from someone's beard, and seeing whether the cutter can cut it the same way a razor would.
Hagaon R' Moshe Feinstein ...
Wikipedia's article on הקפת הראש והשחתת הזקן
מחמת האיסור על המסתפר, אסור להסתפר גם על ידי גוי. מאידך, לרוב הדעות
מותר ליהודי לגלח את פיאותיו של גוי, או של אשה, מאחר שהמסתפר אינו חייב
ואין זה דומה לילד קטן, שאסור לגלח את פיאותיו למרות שאיננו חייב
[במצוות, מאחר שהקטן עתיד לגדול ולהגיע לכלל חיוב במצווה.[51
Because the issur ...
I don't think your friend is correct that standard razors are forbidden because they destroy the hair follicle. Proof is that plucking (pulling) hair manually is allowed despite pulling out the follicle (see here and here).
What is forbidden is to shave "the corners of the head and of the beard" (based on Vayikra 19:27: You shall not round off the side-...
How did our Sages come up with the halacha (or rather idea) that using scissors (or appliances that do not cut the root like most electric shavers) does not constitute 'destroying the corner of the beard'?
And you said the source was:
Leviticus 19:27 states, "You shall not round off the side-growth on your head, or destroy the side-growth ...
Excerpt from a Star K article about shavers:
Hagaon R' Moshe Feinstein זצ"ל was of the opinion that the גמרא 's
statement - איזהו גילוח שיש בו השחתה הוי אומר זה is teaching us that
only the תער , the straight-edged razor, is the Torah's forbidden form
of השחתה and גילוח . Any other method of השחתה and גילוח would be
permitted. Based on this ...
This should answer your question:
The custom of refraining from haircuts during the sheloshim is
generally applied even to shaving, but there is some room to
distinguish between them, because shaving (which is done daily) does
not involve the festive nature of a haircut.
In addition, it is possible that reasons of losing one’s parnasah will
Nit'e Gavriel, Pesach volume 3, chapter 49, has quite a bit to say about this with respect to the semimourning period during s'firas haomer. I'll list some of his points:
2. Included in the prohibition on haircutting is cutting the beard, body hair, and hair inside.
3. One can cut a moustache that interferes with eating, or never-married girls' hair ...
Based on my experience, the general stance on Lev. 19:27 ("you shall not round the corners of your heads") in Conservative communities is that it's not observed, and left to the individual to decide what he thinks of the mitzvah and how he wants to observe it. However, all Conservative Jews I've ever met haven't had peyot; it's just not a thing ...
This is already mentioned by the Kitzur Shulchan Aruch in 170:2 as being permitted with the caveat of not using something sharp as a scraper.
וְאוֹתָן שֶׁמְּסִירִין שְׂעַר הַזָּקָן עַל יְדֵי מִשְׁחָה מִסִּיד עִם אַוִירעם, יֵשׁ לָהֶם לִזָּהֵר, שֶׁלֹּא לִגְרֹר אֶת הַמִּשְׁחָה בְּסַכִּין, שֶׁמָּא יַחְתֹּךְ שֵׂעָר, רַק יִגְרְרוּ בְּקֵיסָם וְכַדּוֹמֶה (נוֹדָע ...
Rabbi Y. Farkash writes in Chol Homoed Kehilchoso (pg 120) that גילוח is not limited to the beard (contrary to popular usage of the term) and includes the hair of the head. In footnote 5 he cites Tosfos Moed Koton 14a "Umenuda", as well as bringing your proof that S.A. and poskim uses the term גילוח by a minor.
This answer is not an Halakha
The issur of shaving needs two conditions :
to destroy the hair
to use a blade
Since the laser is not a blade, it could be allowed to use it. As it is allowed to use depilatory cream.
However, there are other reasons to not remove one's hair. You can see this link for further details.
Shaving only the mustache but keeping the beard may make a person appear to be Amish, which might be chukat akum (Vayikra 18:3, Rambam (Sefer HaMitzvot Lav no. 30), Sefer HaChinuch (n. 262)). All the moreso because the Amish do so for religious reasons.
The Tur in Orach Chaim 531 quotes Rabbeinu Tam who opines that one who shaved before the moed may shave on chol hamoed as well. The Tur strongly disagrees and seemingly all subsequent authorities were stringent. In more recent years this idea of Rabeinu Tam has been suggested again, but the fact that Rabbeinu Tam already said it and was rejected and ignored ...