A reminder: @newpeople, using @username as a form of reply is discouraged on @MetaFilter. This isn't @twitter.
You are more than free to do it, but know that about 3/4 of the people that read what you wrote are not impressed. In the least. We have a few conventions here, and not using @ to reply to someone is one of them. Try instead:
That isn't so hard, is it?
Posting because this behavior has ramped up the last few months, and this needs restating.