<p>Personally I leave "thank you" statements or the like. It is nothing that clutters up the question and at the end of the day it's nice if people are friendly. A different thing is when someone has a lengthy introduction which is about anything else but statistics. Fortunately this rarely happens.</p>

<p>I've never seen anyone starting their answer with "this is too simple for this site" or likewise statements, though I'd apply the same rule of thumb as before: if it clutters up the text due to excess length then it has to go. Otherwise I would just leave it even though I think it's not very polite to begin an answer this way. What is a trivial problem for some users can be a huge challenge for others.</p>
