Is HERMIONEGRANGER09 a good USERNAME?

IDK

No. No, it isn't.

For one thing, it's very derivative. Also, nobody likes Hermione because she is a teacher's pet and a know-it-all.

Yeah it s a cool name...

That sounds a lot like me. I think it would be a good username.

Nothing, so long as you are gracious with it, which Hermione is not.

Are you just mad about her being so intelligent? 

No problem.

Sure

I'm not mad about anything. I haven't read the HP books but I've seen the movies, and Hermione is portrayed as a teacher's pet and a know-it-all. Lisa Simpson is just as intelligent but lacks that unlikeable know-it-all quality. I have to say that Hermione did become a more likeable character as she got older, but the OP's username references 9, so I assume Hermione aged 9 is the version we are talking about here. And Hermione aged 9 was not likeable.

David Bowie.... (who wrote a song called....letter to Hermione)

...in the 60s! That man was so far ahead of his time.

This a picture of the real Mozart...at least people say it is

This is NOT Mozart

I got the threads mixed up...that was for the composer chat

Letter to Hermione was Bowie with a broken heart who wrote a farewell letter

Back to Hermione with the cool name...

Don't settle for mediocre copying of others' ideas. Come up with something original for yourself.

Well, you can choose any username you want, I mean, it’s your choice, no one can stop you @Hermionegranger09

No, because it's an anagram of Hermann Goerring.