I am more worried about some dedicated reddit, or 4chan user getting angry than the feds. I'm weird with this because when I write posts I wait 2 minutes, and think how would feds interpret my posts, and is it worth posting that.
I will most likely make a mistake with my anonymity one day, but to have alts increase anonymity wouldn't you have to be good at changing your writing style?
Creating new alts helps you avoid the crazy reddit/4chan people most of all. It's questionable if it works with Feds tbh, doubt it hurts though.