Yes, I sniff too. But I am not always sure if it's a tic, or if I sniff because my nose is always running. I think that sometimes it's a tic, and sometimes it's allergies with me.
Selective mutism is most often a part of autism, rather than stemming from a social phobia. A lot of people on the autistic spectrum have tics as well, and can be misdiagnosed with TS, or they can have both, like me (it's a matter of severity I guess, all autistic people have some tics, but not necessarily as many as me).
German citizen, married to a Canadian for 28 years, four daughters, one son, eight grandchildren (and one on the way).