It's almost like MN's design team don't realise that the norm has moved on massively from 20 years ago. 20 years ago when forums were the main thing on the internet, all posts being in line, and Reply going right to the bottom to save your finger from scrolling on a longer post/loading a million pages, were normal and expected and so people who are familiar with those norms will have understood that, and might retain that understanding even if they came across MN for the first time today. (Though, honestly, even then?)
I admit to being a web oldie and loving/missing the golden years of forums before social media took over. I really value that MN still retains this format because I think all posts in line is a very good format for discussion. I could expand on this but it's off topic. Anyway, it's a GOOD thing that MN has this and I don't want to see it change.
But people who regularly use the internet today are more familiar with threaded discussion, like FB or reddit or twitter or basically every other thing on the internet now, algorithms which simply bump the "best" threads to the top (
) so scrolling isn't necessary anyway, faster internet so no need to limit the amount of data being loaded by using pages, and the idea of a reply button individually on each post all going to the same general place would seem redundant, so you'd quite naturally assume that reply being on every post will mean that this is some kind of targeted reply to THAT post, whether threaded or tagged or quoted. The one they see most often is quoting, so they likely assume that is what it will do.
When they see that the quote does not appear on their own thread, my guess is that they then assume oh, it's just me who can't see it. I can see everyone else's quotes, so they must be able to see mine, even though I can't. Because, again, they are used to more dynamic modern social media sites where what you see is different from what other users see.
It's not that the format of MN is wrong, but the button is misleading because it's relying on outdated assumptions people haven't had for about 10 years. Because the norms have changed, it makes sense to change the prompts for users in response to that so that they behave in the way that current users are likely to expect. Especially if you change the layout to make it LOOK like it's not a clunky 1990s forum. Because when you go on those old, 1990s/2000s layout forums, the reply button makes sense, AND they have all the quote/thanks/etc directly on that post too and it doesn't look cluttered (any more than the layout looks cluttered because it's dated).