On our default #general and #offtopic channels, messages just triggering notifications if mentioned, although mobile/desktop notifications are set to trigger on all messages. Still present in 0.60.x

Guess:
Maybe this is a bug caused by Slack import, I'll check my files (but they are older than one year, so have to search for them) Settings for notifications are not included in Slack export files, so they can't influence this behaviour. I'll have a look into the mongo, but my guess is, that this will reveal nothing helpful.