I can only give my opinion, not policy! :). I keep a short version of the gedcom import nottice under acknowledgements to help with keeping track of where the profile came from, etc. (easier than looking through Changes). If somebody did something special (e.g., flew to England to get a copy of a will to post), I would keep an acknowledgement for that. And I sometimes put sources that aren't real sources there (too subjective to explain simply). I don't like keeping acknowledgements for the routine stuff we all do.