Tom, I personally use the guestbook mode, although the single message option is the default, as you noted. I'm pretty sure there's a way for me to change the default display mode, but I never have tried. If you register a profile, our system sets a cookie that remembers your preferred display mode, so you don't have to change it on every messageboard and computer (or device) you use.
In the old days, some people resisted registering because of presumed spam bots that would vacuum up addresses and bother you forever. Those days have effectively passed, as our developers built in a lot of safeguards about 8 years ago. Maybe it's time to register. Text formatting and file uploading are two additional benefits.