I often respond to things I get quoted in. Usually I'll check the page the quote was on, the OP, and the quote I'm going to be posting on (40 ppp ftw), but often, a buried thread warning that is still active, might not even be visible. If folks are expected to abide by them, there should be an effort made to make them visible for those trying to do basic due diligence, don't you think? Especially given that the search feature on this website brings up thousands of unrelated posts before it does anything you're actually trying to find related to any possible thread warnings?
I suggest:
Best case: display the post with the thread warning at the top of each page
Realistic case: add the damn thread warning to the top. It's five clicks and a ctrl + v. Mobile it's five taps, a long press, and another tap. It really does not add that much effort to a mod's job.
Assuming a typical moderator gives fifteen thread warnings a day (extreme case scenario), it adds maybe a minute or two a day tops, and helps keep active discussion from straying.