Respond with a message like:
Looking for an invitation? https://lobste.rs/about#invitations has an intro, and https://lobste.rs/chat explains some expectations for this channel. (I am the channel bot.)
This doesn't need to remember if a username has ever been in the channel, ten minutes since they joined is fine.
Respond with a message like:
This doesn't need to remember if a username has ever been in the channel, ten minutes since they joined is fine.