Or should that be lmposters ...
I reported a post by someone who had subbed an uppercase i for a lowercase L in a username - it looks pretty much indistinguishable. Obviously the rightful owner has posted that it's not her and reported too. You can see what's going on if you happen yo use the flyover on the browser version but that doesn't exist on the app.
The matter came up a while ago (there was a fake BertrandRussell on the same thread as the real one, in that case probably innocent but confusing) - I think it was raised with you then. There might be ways to filter new names to make sure they weren't old names with very similar appearance, but just displaying the username in a clear serif font would help.