Lot of the time everyone is in such a rush to leave either I can't move fast enough to comm someone before they're all gone, or I comm the one person who's left to comm (if their play was adequate )

On the other side of the coin, I collect random comms for the same reason - I'll be slow to exit the duty and I'm sure I get commed for being the only one left to comm!

I will comm DDs most especially, when they show leadership in duties - taking on the role of explainer, when the Tank is a first-timer, for example.