A new user asks their first question and someone comments first with **just** "Welcome to [stack exchange site X]". 

The comment was made *only* for the purpose of welcoming the user to the site. They do not say anything about the question at all and do not contribute further after this comment.

Although such comments might be encouraging to new users they do not contribute to the question in any way. Should these be flagged, and if so with what flag? It seems that in these cases where it's not followed by some more constructive info, it could fit under either non-constructive or too chatty.