I reached trust level 3 and yesterday found out by coincidence that I lost it again.
Discourse won’t tell you what you need to get a higher level (not that I know of), but it also won’t tell you when you lost it. I found out because I tried to edit a topic’s category, but the option was gone.
This is very inconvenient: what if you have a topic going on in the Lounge category? You can’t go back.
It turned out my reading percentage wasn’t high enough anymore. But what about vacations, etc? You go away for a while only to find out you lost access to certain things and you have no idea why (this time @codinghorror told me what the reason was).
And come on, I’m not reading enough?