Answered by Alex Beam:
I feel comfortable answering this question because I have a number of eccentricities: I often talk to myself; I sometimes greet people with the words "Woof, woof" and (VERY occasionally) answer the phone that way.
Any clinician will assure you that tics like these -- I often tap walls a few times as I pass them -- are quite harmless. They may appear at the lower end of a continuum that leads to so-called Obsessive Compulsive Disorder, or OCD. For instance, if I were unable to leave a room until I had tapped each wall three times, I would be diagnosed -- correctly -- with OCD, meaning that the tic had become a serious impairment.
And a clinician would emphasize that schizophrenia, or variations thereon, would have more serious symptoms, with much more serious consequences. Auditory or visual hallucinations, for instance, of the kinds that John Nash experienced. And, they prevented him from participating in his domestic and professional lives.