###Canned responses
I don't speak for others. I do however consider it useful to have stock comments. I call them canned responses, which I often tailor to specific users. I check out user profiles to see if the user already knows the SE culture in general even though they're new to the site.
###Welcoming new users
Although it's not mandatory, I think it's only natural to preface our comments with "welcome to [sitename]" when we see new users. I have been doing so for 4 years on any site I frequent (especially ELU). Considering that this is IPS, it makes even more sense to be friendly to new users.
But here's the thing though. I don't necessarily suggest being okay with poor quality posts or turning a blind eye to bad things happening just because some user is new.