So, I got a Weedle. Why a name like HashtagBEAST? Beedrill learns very awesome moves.
However, why is it banned?
I know why.
I tested it in the game, and now I'm pretty sure why. The name contains the word 'sht', which is basically that swear word without the vowel. Of course, giving the name a space is quite impossible as it reaches the exact limit of 12 characters, so you may not be able to give your Beedrill it's desired name. Sorry. :(
Hope I helped. :)