And it can always be worse!
Believe me, I understand how people can wrestle with unsightly, unsanitary and annoying habits. Just ask my husband about my tendency to pick at my cuticles (without being aware of it) while we're watching TV. It's disgusting. I know this. And while I sometimes catch myself doing it while sitting through a particularly mind-numbing lecture, as soon as I catch myself, I sheepishly put my hands under my desk, or start frantically writing down whatever the instructor is saying (even if it's something like, "This weekend my daughter said . . ."). Also, I know that I crack my knuckles. This was another habit I didn't even know I had until a boss from my previous corporate life said (during a grand-old knuckle cracking spectacular) "That's disgusting. Don't ever do that in front of me again. It's just like passing gas (I kid you not, he said this!) - if you have to do it, go in the bathroom." Now, ironically, since he pointed this out (6 years ago) I am extremely skeeved out/irritated/nauseated by the sound of other people cracking their knuckles, all the while I am just itching to crack mine.
But. Thumbsucking? In college? And not just in your room, while you're trying to fall asleep and only completely freaking out your roommate, but in class?!?!?!?! My advisor mentioned something about SBH students in elementary education settings (Severe Behavioral Handicap), but later reminded me to remember the PFNs. Plain fuckin' nuts.