Upon rereading the rule, and checked out El Barto's posts (since I don't ever read that thread), while it's certainly not necessary to use that language, I personally find it reasonable. But that's a subjective and arbitrary assessment, just as the rule itself is.
And I think that's the issue here for me, that it is a subjective issue based on context, so it's hard to try to draw a line, or in this case, try to redefine that line. In general, I feel swearing is mostly fine unless it's used as strong language aimed towards someone personally etc (like if I said "F you"). I've been told off by a mod once for tamer words used in a similar context, which was justified, so it is very judgement based.
But in Barto's particularly context, I don't think it was excessive as it relates to the forum rules. Just imo of course.
Is this not what the forum filter in the options is intended for? I have no idea what words it filters, since I've never used it.