Dear Welcome to HCM We understand your concerns I went through your description. I suggest you not to worry much. From the given details, it is not possible to diagnose your friends problem. So many people have peculiar mannerism, mannerisms which comes forth only when they forget themselves or concentrating on something. The odd behavior or gesture from your friend could be one such mannerism. To be sure you need to visit a clinical psychologist. If you still require my services on this aspect, you may post a direct query to me on this portal. Please include as many details as possible. I shall provide psychotherapy treatment tailormade for you which should help you good. Hope this answers your query. Available for further clarifications. Good luck.