When designing your RSS feeds, the top level title should be the title of the user's account. So if Bluesky had a feed for each user, the channel-level <title> element of the feed would be
<title>Bluesky: Mark Cuban</title>
Why? Well because readers need context. And it's easy.
And feeds are showing up in places where there isn't much room for the titles, so you have to make your characters count.
Bluesky shows the user's address, imho it should be the string the user chooses for their presence on the site, usually simply their name.

Arrow points to Mark Cuban on Bluesky. That's what the title should say.