look at the traveler's (or host's) posts to see how long they've been a member and read their posts (a fantastic measure of how interesting or obnoxious the potential traveler may be)

It's a good measure of "interesting" but a poor measure of "obnoxious". I've ended up meeting a lot of people that I first knew online: while you can get a good measure of someone's intelligence, verbal cleverness, and interests from text, a face-to-face meeting has much higher bandwidth when it comes to mannerisms and social skills, and the change in register can often mean a significant change in the tenor of your interactions. That can easily lead to finding new and interesting ways for your friends to be annoying, much as you can be friendly with someone for years but conceive a passionate antipathy within weeks if you decide to become roommates.