Oh sure, as I said, at the IKS we use Discord very effectively for huge, long running play-by-post games, D-Day with 96 players for example.
Hm, the military context might be something. Although, we also have a number of those folks on the server, and they have run and played games with us. So maybe not as much of an issue as one might think.
It's just that I think it offers so many features and options that make it so much more convient to use for these kind of games than e-mail, and that I don't believe in "that's how we've always done it" to be a valid argument for anything, really.
But enough preaching for now.