If one eats at a restaurant, but eats outside where there are tables and chairs, does that invalidates one from testimony? Are there any poskim that address eating outside at a restaurant?
I found in Sefer Devarcha Yair 2:34 who discusses this issue in depth bringing all sources. If you want to see all the back and forth see the teshuvah inside.
His conclusion :
- It is not proper for a Talmid Chacham or Ben Torah to eat in public even if its an area with a small amount of people. So too they shouldn't drink even water in public.
- For a regular person it is prohibited to eat in a major public area(main street) even if it isn't a gluttonous type of food. Nevertheless , if one did eat in such a place they do not lose their status of being a kosher witness since nowadays people do not view such eating as prohibited or degrading.
- In a place where it is common to eat in public such as a bus, or restaurant it is permitted even for a Talmid Chacham to eat in public.
Rav Meir Mazuz in hi Mekor Neaman was asked if one eats a set meal in a park is it considered like the prohibition of eating in public? He answered that if one sits on a bench and eats in a respectable fashion then its permmisble.
Text of Devarcha Yair 2:34 :
Text of Mekor Neaman 1:275 :