For the issue you linked? Like it said:
It can’t get any clearer, or any more defined than that.
The looser definition is when you’re using the correct channel, but might be doing it too often. Yes, your realmmates do have a say in that…through reporting. If Blizzard thinks it’s borderline, but players on your realm are constantly reporting you, then they may make a determination to action your account. Likewise, if they think it’s borderline, but it’s one or two people reporting you a single time, then they may let it go and not action your account.
No, Blizzard is not going to clearly define anything, if only to make sure players aren’t doing an end around the rules. If you have any concern that you may be reported, then that may be a sign to slow down. If you are getting warnings, then that is definitely a sign to slow down.