I think I lost my Regular badge after a period of inactivity on the forum 
I can still see the notification from when I earned it in March in my history, but the badge no longer appears on my profile. Is this expected behavior, or could something have gone wrong?
Googling, I ended up at Understanding Discourse Trust Levels
To get to trust level 3, in the last 100 days…
- Must have visited at least 50% of days
- Must have replied to at least 10 different non-PM topics
- Of topics created in the last 100 days, must have viewed 25% (capped at 500)
- Of posts created in the last 100 days, must have read 25% (capped at 20k)
- Must have received 20 likes, and given 30 likes.*
- Must not have received more than 5 spam or offensive flags (with unique posts and unique users for each, confirmed by a moderator)
- Must not have been suspended or silenced in the last 6 months
So it looks like it’s expected.