Needs citation.
Debian stable uses upstream LTS kernels and I'm not aware of any heavy patching they do on top of that.
Upstream -stable trees are very relaxed in patches they accept and unfortunately they don't get serious testing before being released either (you can see there's a new release in every -stable tree like every week), so that's probably what you've been bit by.
You're right stability comes from testing, not enough testing happens around Linux period, regardless of which branch is being discussed.
It's not easy testing kernels, but the bar is pretty low.
You can do that well enough with Debian's "testing" and "unstable" release channels. Aside from the few months leading up to a new "stable" release, which usually isn't a big deal (and fixing regressions in "stable" should then be a higher priority anyway). Just don't install it on systems that you actually depend on to keep working. But running it on your desktop at home that you only use to play and experiment with is just fine.
The wiki has more info on this.
https://wiki.debian.org/LTS https://wiki.debian.org/LTS/Team https://wiki.debian.org/LTS/Funding https://wiki.debian.org/LTS/Extended
Whether that qualifies as "heavy" or not is of course a matter of opinion, but it's not nothing.
