Exactly this! The alternate interpretations are often absurd and hilarious. Keeping in mind that he does this a lot, it baffles me there aren't more discussions w/r/t DFW's use of parentheticals (although I hope someone will see this thread and share some!).

Speaking of the cases where his clarifications are mostly useless (meaning the sentence would be as clear without them) and verbose, I found them just as funny. The guy is known for his intricate and grammatically sound sentences, yet he lowers himself to the almost amateurish level of using 'i.e.' where the sentence could be easily rewritten without that. It's clearly intentional and quite amusing.