Following is a brief and friendly exchange of comments which was flagged twice by users for being "too chatty", and "totally irrelevant" as one put it:

2 @Max Alekseyev, congratulations on the Riordan Prize. – Fred Kline 4 hours ago

2 @FredKline: Wow! This is an unexpected place for congratulations. ;) Thank you! – Max Alekseyev 32 mins ago

Strictly speaking, those comments are indeed irrelevant to the topic, and so they are about to be duly deleted in response to the flags.

However, I find it a pity that a note of congratulations and thanks in return are so urgently hit with flags. Such comments are harmless and contribute to a generally friendly spirit which is sometimes missing. I'd feel the same way about dealing with a good joke in a comment: yes, technically such might be considered "too chatty" according to SE guidelines, but who cares?

Plus, I was glad to have learned in this way of Max's winning the Prize, and would like to second those congratulations to him.