I have not gone to see the thread where the OP’s issue arose.
The title of this thread is about highlighting. The substance of debate in these first dozen-ish posts seems to be about body-shaming and whether some post(s) arose to that level. With a side order of arguing about misleadingly-selective quoting.
So we seem to have 3 topics at issue here. I’ll speak only to the title issue: highlighting.
If I want to highlight a part of a snip, it’ll go like this (and deliberately choosing an innocuous post as an example):
Bolding mine.
You know, it’s actually possible to fold any bill that way. The difference is whether the result is a mushroom, or a fir tree, or a field of green depending on who’s head is on the bill.
The point is to call out what I did in the very first sentence below the quote and to have that as a free-standing paragraph. Anyone missing my caveat isn't paying enough attention. That's (IMO) 100% on them, not me.
I’m also cautious to not add bolding or italics to a snip that already has those features. Since very few people use underlining here, I’ll use that if I have to add my highlight to something that already has bolding or italics.
As a separate matter here’s an observation about partial quoting.
Back in the vBulletin days most of us where pretty darn reliable about starting or ending a quote with ellipses if we were not quoting the entire post. ISTM that about the time we switched to Discourse that habit dropped off. Now it’s commonplace to see partial quotes with no indication they are partial. Such as what I just did with @Thudlow_Boink’s post where I snipped off the last half with no indication of having done so.
I suspect that change was triggered by the ease of partial quoting in Discourse, a feature vBulletin lacked. In vBulletin you had to quote (or multi-quote) the whole thing then manually delete the bits of someone’s post you didn’t want to include, which facilitated remembering to replace the removed portion(s) with ellipses.
As a result, our current culture doesn’t quite align with our rules on this narrow topic. And other than when (possibly mistaken) accusations of bad-faith snipping crop up, this doesn’t seem to be a problem that needs addressing. But might benefit from a bit more diligence on everyone’s part.