Agreed; you need some work. Some of your comics have funny bits at the beginning, but end badly because you don't know what to do anymore. In "Teenage Boys", the real punchline is on the left in the second panel. Don't feel like you have to use every dialogue bubble... if you've only got three lines, for example, put one in each panel.
Your Penny Arcade strips... I don't know what the deal is with them. They'd be unrecognizeable as jokes about PA if you hadn't told us they were supposed to be. Some of your other strips have the same problem... they seem to be making fun of something, but I can't figure out what it is. My advice is to think harder about what's funny about your subject before you start writing.
These comics show some wit:
[Click to view comic: 'Chat Room Beginner']
[Click to view comic: 'Teenage Girl's Christmas!']
Both show good structure and end with an actual humorous punchline. The latter, in fact, is funny throughout.
Keep at it, and good luck. Oh, and don't rewrite your comics with your new account. Just put a link to the old account in your profile or favorites.
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The what mentioned above is total fiction. Please don't take it seriously!