that's intended (because you're subscribed to a "kbin mirror" of the OG community if I got this right)
yes, "@FirstSeaLord" or for lemmy instances "@example_user" (didn't want to use an actual user name here youknow)
idk, probably/hopefully?
yes, under settings/general/appearances you can change that.
edit: what I'm personally waiting for is the opportunity to search with wildcards. So like "@news.*" for all lemmy instances with communities named news.