But if one is going to use an actual swear word (that they're wielding themself, rather than quoting), why pull one's punches? IMHO, maximum condemnation is to spell out all four letters. Unless your intended message is that something is highly despised, yet could be worse, so you're keeping the final letter in reserve.

Oh, though, if it were an in-person demonstration sign in public, the kind that's for an audience of broadcast TV news cameras, I suppose maybe self-censoring the word might be more likely to get it on the air? Or at least that could be the thinking? And someone mimics that in a different context.

Or it could be someone raised not to use strong words, and to be apologetic when they do, and so then the apologetic signalling could mean, "I don't normally use strong words, but this is so bad that even I felt compelled to do so, despite my respectable sensibilities".

Or it could be a non-culturally-fluent speaker, who's learned idioms, and picked up these ones, but hasn't yet been exposed to some of the finer points and connotations.