The Mom for a great story by a friend of mine). I think the comments and people's nasty wet thumbs are part of the penance of Ash Wednesday.
"...in the books both in the Old Law and in the New that the men who repented of their sins bestrewed themselves with ashes and clothed their bodies with sackcloth. Now let us do this little at the beginning of our Lent that we strew ashes upon our heads to signify that we ought to repent of our sins during the Lenten fast" (Quote here.)
--St. Aelfric, c. 8th century.
This is the day, after all, that we remember "That thou art dust, and unto dust you shall return." No, it is not a holy day of obligation, but it is definitely a beneficial reminder of humility and mortality. Go to church!