I'm logged out by default and only log in to comment, which is rare. I don't like leaving my username up for display if a friend/family member has to borrow my laptop for something. I've engaged in a couple of communities that are a little more counter-cultural than my peers.
Done this. Eventually one account always becomes my main account and I'm back to square one. I don't care enough about reddit to keep up with 2 separate accounts.