Pretty much how it has been for me for both lemmy and mastodon. I think I went to the sign up page for mastodon several times in the days that it was blowing up, and I just didn't know what server to pick, and even when was at the point of "I will just join one" I still had issues picking one because a lot of the site names sounded untrustworthy, or like specializing in a community I am not really part of. Like the one I ended up on gave me vibes of being for people into astrophysics.

I am also not sure if people would read the rules pages, but more skim them for keypoints in maybe 30 seconds. Think went that route with lemmy that I skimmed the rule of a potential instance and saw the rules and went "nope, not for me" and was back to step 1. Though this time I was more familiar with the rodeo and have made more users on more instances

Depends on what one are using to browse lemmy with. I'm currently using voyager and it seems to show all as just their username, but for example now while replying to you, it shows that I'm replying up electrogamerman@lemmy.world, so I could use that to differentiate you from electrogamerman@lemmy.ml in that way. But no way to confirm if the lemmy.ml is just you on a different instance

As long as nobody has already taken it on the other instance you can reuse user names.

Had the same problem, and someone pointed me to lemmy_migrate by wescode on github, and it worked well. Although it do require a recent version of python installed