That's been a setting for a couple of years, if not longer.
It was implemented because there were too many occurrences of nested quotes as deep as 10 or more, making posts unreadable.
While part of the problem is the way in which post buttons are presented, the "Quote" button tends to be used as a reply button when most often, there is no reason to quote an entire post (especially when it's immediately above a quote of it) - or the quotes of quotes of quotes of quotes of quotes...
There's a convention here which has developed over the years: starting a post with "^" indicates it's a response to the post above (if it's not already obvious), and "^^" to indicate the post before that - but really, it's better to trim a quote down to the part the response is intended to address.
_________________
Giraffe: a ruminant with a view.