I'd say the majority of the talk on the mat at my dojo is either typically questions of how it felt/did it feel correct/am i stepping too far/etc, and a few jokes. We don't really have anyone trying to improve on what has been said regarding the technique, with the exception of some higher ranks helping out the lower ranks with understanding of some things that they are missing. The extra help shows up magnified in the basics class of course, but that's only because it's needed moreso there.
I honestly haven't seen lower ranks trying to correct upper ranks after a year of training. Personally, I think that it'd be rather disrepectful to do so. Well, unless it has something to do with what uke is feeling.. then I could see a lower belt saying something like, 'I really don't feel any tension when you go to do the technique; that may be the problem' or 'when this happened, it killed my momentum.'