I think there's a component where the words matter and the intent/inflection/tone matter and that combination can be used as a whole.

Also, the desire to comment to the world when things happen is pretty human.

"That was unpleasant and hurt" when you smack your thumb with a hammer could come out as a variety of things, such as: "fuck!", "ow!", "Jesus Christ!", "yikes!", "damn!", "aaaiiiee!", etc. Are these ALL swearing, or does the word matter? I would say it does, but we may disagree.

But I think the intent is the most important component for me. If my kid says "fuck" after smacking his thumb, that's not going to bother me. I'll ask him to code-switch around me and use something else, but I fully expect that his friends are cursing all the time. The code-switching is the lesson, not the word.

If he says "fuck you" to someone, that's a different scenario and the words are actively hostile. It doesn't really matter what the words are, if the goal is to hurt someone verbally, then it needs to be reasonable and sometimes it can be. Telling a bully to "fuck off" won't bother me, telling a teacher to "please depart from this facility" would. Some of the best disses in history were made without swear words, but were devastating because of it. Be eloquent.

The grey area for me come in when the 'swear' is an adjective. I try to coach my kids to not do this, but it sometimes happens in my speech, and I don't bother with it in text when I can assume my readers are old enough to code switch: "These legos are fucking stuck together" is not acceptable, nor is "these legos are frikkin stuck together", but "these legos are really stuck together" is. Sometimes, though, you need the extra emphasis a swear word gives you.

My kids read the good books, so sometimes they'll pull a swear out of a novel. Brian Sanderson has a whole pile that my oldest will sometimes use. I find it charming when he yells "Storm it!" when I tell him to go brush his teeth. Maybe that's just me.