There are some weird people about. I used to post on a particular dog breed rescue forum as we had a dog from the organisation. They had a weekly chat room and someone logged in with a very similar name to me posting vile stuff whilst dropping in snippets of information I'd put on the forum to make people think it was me. I name change all the time for that reason.
I meant really similar like adding a letter. Cheesesarnie/ cheessesarnie. So it wouldn’t show as username taken when they registered but would be confusing. Lots of similar ones (as you say dragons, cheeses etc).
We did have a spate at one point - we've not had this problem for a while though. It doesn't look the poster will be back, but we've zapped the post now and if you've any other problems at all, please do let us know