Generally, I try not to say anything when I see something dweebish so as not to start anything. As a rule, I'm not interesting in baiting or griefing anyone for my own enjoyment. Though, on occasion I'll see something really out of the ordinary and just have to make a probing comment about it. I try to make sure it's not insulting or really confrontational, as I'm usually just trying to find out what was that guy thinking. However, it's hard to do that and not salamander someone's ego, but I try.
Depending upon the response I get will determine how and if the conversation proceeds. The greater majority of the time, I get a sometimes angry, but usually only aggravated reply that has some explanation or reasoning about it. From there I usually make friends and have a good converstation.
Now, when I see something really, really dumb, and after I kill the dude, I check the roster and if he's got a score in the serious 4 digit range, I figure he's new. I will usually PM him and ask if he knows what it was he did wrong in our engagement. If I get any kind of reasonable response, I will offer to tell him and even to go to the TA and show him. Unfortunately, more times than not, the newb is either too embarassed to even answer or still doesn't know how to PM or respond on 200. LOL