last time I checked, anyone can use /whois, I use it to use /tpa, since I have trouble remembering the spelling of people's usernames.
edit: I also recently found out a fun hole in worldguard; if you place blocks while jumping on them in a place it doesn't allow you to place blocks, you can still jump around a bit using them, and using that, you can jump over most walls meant to contain you, as long as there isn't a ceiling.