Comment by Mickydtron

I agree that that's probably how it started, but it seems that once the cultural expectation has been set, it's hard for a single project maintainer to set a different custom just for their own project. People are going to use the conventions and communication methods that they learn elsewhere, even if you say not to in the contributing guidelines document. You might be able to get individuals to stop doing it in your project by asking them directly, but then each person has done it at least once, and you've had to ask each person to change their normal habits. Besides, as they note in the letter, there is a valid and valuable purpose to these communications, it would just be better if they were in a different place than clogging up the comment thread.