If the community does not have a follower, new activities may not be sent. For example, you can check [email protected] which is more mainstream community, they're federated.
There is auto complete on default UI, I can just type “@postw” and it’s showing me the bot. I’m not sure about bookmarks but they should implement auto completion on their apps.
TBH they couldn’t handled the traffic at the beginning because Lemmy wasn’t stable as is now, but I believe they tried their best. Also I can’t say for all of them but their admins are reliable, trustworthy people.
I usually get errors close in size to this but at the moment I had a diesel to send. I kind of figuring out the problems but it takes time and a few hairs :)
Voyager app has that feature on its settings page.