I can't even articulate how disgusted and irritated I am when someone in my presence is doing any of this shit. I mean, what the fuck are you supposed to say when someone has the audacity to continue biting their nails in front of you? I can't think of a single way to tell them to stop, respectfully.
For all of you proclaiming you can't control it- that's complete bullshit. You can- just exercise a modicum of willpower, and stop doing these nasty habits. You'll be frowned upon in any social or professional environment, and will disgust people. It also displays a lack of self awareness which is extremely unattractive.