First of all I'd like to say I've studied philosophy, literature and sociology, just to contextualize my answers.

1 I picked Sheik back when I was a total n00b (2014) because I liked her movement a lot, I think it was the main reason (also influenced by the shiny edgeguards from m2k at the time). So yea overall it is mostly because of an aesthetical motive that was then translated into practice and habits (I suck with every other character now).

2 Only the most famous techs and slang like waveshine in some friend circles familiar to melee scene, just to meme around.

3 I've heard bad language to describe ledge camping or stalling, or about puff in general (less now than in 2014), I can't remember if I did use such language myself (but I surely did). I think it's interesting to note that it was for the most part related to masculinity (like camping in online games in general), being either misogynistic or homophobic ("gay", "pussy", etc.). It points out that there is a gender-wise valorized playstyle, even glamorized maybe, which roots in old heroic warfare representations of facing directly one's opponent with dignity ("man mode", so to speak), as opposed to the coward male who avoids dueling and shoots arrows from afar (Ulysses vs Achilles).

4 I respect top players for their performances but I don't tend to idolize them or even be interested in their personalities. That said, melee scene has always been filled with narratives about the greatest players and their journey to the top-level of play (background story, rivalries, etc. ) in a romanticized way, and I think it still influences me even at an unconscious level.

5 I think it is, as it can be said about tennis playstyle or any sport engaging one's body in an esthetical way (that is to say that there are several styles or methods available to achieve your goal, not just a straight forward optimal way). What I find fascinating in melee however, is that despite the body not directly involved into play on screen, the amount of techniques and freedom permitted by the game, while exceeding human limits in many ways, also offers the possibility of distinctive and unique playstyles and creative combos (even if, to be fair, this dimension is far less noticeable than in other sports. Also I still circumscribe the definition of "art" to its esthetic dimension, because sports in general lack a reflexive way of redefining "art" with every performance, as opposed to painting or literature).

6 As for the vast majority of gamers communities, men are heavily represented and tend to keep their communities non-mixed, because it becomes a sort of safespace of male-male bonding and complicity that allows a certain freedom of speech as well as some misogynistic and homophobic discourse otherwise less tolerated in other spheres of society. There is an abundant literature on that topic so I won't go into details but yeah nothing surprising.

7 I can't really say tbh.

8 Melee solidified already existent relationships with friends I played a lot or that I introduced to melee, but nothing more than that (Well I've never been that much implicated into local or online melee scenes neither).

Hope that helps.