As hats are more commonplace than the Queen, I'd sooner assume he meant holding them than her at weddings :)

So it's mainly an issue of writing. Perhaps (I guess) also of muktzeh.... as both selling and buying would involve handling (acquiring) an object needed only after Shabbos while preparing for another day, unless you bought something for use on the day, which would then not have been prepared (in terms of ownership) beforehand and also muktzeh?

cont. "Incidentally, even though acquiring things is normally forbidden, someone who finds an ownerless object on Shabbos may keep it, provided, of course, that he does violate carrying or muktzeh (Pri Megadim, 371:7 in Eishel Avraham; R' Akiva Eiger, glosses to Magen Avraham 339:6; Sdei Chemed Vol. 2 pg. 220). Since there is no buyer and no seller, Chazal were not concerned that he would write anything." (yeshiva.co/midrash/shiur.asp?id=10813)

Oh, here Clint- "Chazal... prohibited selling or renting items on Shabbos lest someone record the transaction (Rambam, Hilchos Shabbos 23:12). Similarly, it is prohibited to weigh or measure on Shabbos (Rambam, Hilchos Shabbos 23:13), to marry (Gemara Beitzah 36b), to perform a pidyon haben (Shu"t Rivash #156; Shulchan Aruch Orach Chayim 339:4), or to make financial calculations in one's head (Rambam, Hilchos Shabbos 23:18). All of these are prohibited out of concern that one may forget and jot down some of the information on Shabbos."

Re the title, what's the difference between choice and decision?

Can't DNA tests sometimes determine whether results are matrilineal? I don't know if it could give the results about whether you are Jewish through the mothers' line though. Also, to fully answer your question it would be worth getting an answer about what happens if a person could find out through DNA testing that their mothers' line is Jewish, and yet they don't have a family tradition about it. Would they be automatically obligated to keep Torah, or would they have a choice whether to convert? Anyway, remember that anyone can become Jewish, and many people choose to because of ancestry.

I don't understand the ruling here. It says 'in your houses', not just 'in your possession'...

Mm, thanks. What advice would you give to someone choosing a tradition/community to start with? I feel that some are compromising too much and some are adding too much, but it's hard for me to tell.

Thanks! I like this answer. When you say "the rules for deriving laws for situations not explicitly covered in the written torah"... does that really cover all of the small details, e.g. how long you have to say a bracha and eat, or how much you need to eat, and such? I value the way Judaism makes rules rather than suggestions, for the community... but can it be articulated why things such as these matter, actually, in the system as it is?