Yes, for example Youtube video links are copied with the &pp= tracking information. Search for something on Youtube, right-click on a result title, and copy with or without tracking gives you the same thing (with the pp=).
That feature removes parameters that are known to be used for tracking. It does not remove all query parameters willy-nilly. For example on youtube it should remove si, feature and kw parameters as well as a set of parameters on a list that applies to all websites. However, pp parameter is not in that to-be-removed list.
As an example v parameter is for video id on youtube, it would be kinda silly if that was removed, so the feature kinda has to do some site specific action.
pp has been introduced 3 years ago and it's a known tracking parameter. And it's not some obscure website we're talking about, it's the largest website in the world...
If they're not going to keep up with parameters after so many years I think it's very misleading and potentially even harmful to keep offering this feature.
All I'm saying is that it leaving some query parameters unremoved is not indicative of the feature not working. If you want to add more query parameters to the removed list then feel free to open a bug about it.
I get your point, but this feature is being pushed to users prominently, and it turns out it doesn't do anything with the search results on both Youtube and Amazon, which are pretty much THE most likely sites you could think of, that anybody's going to be using. That seems like a pretty glaring omission to me.
There are lots of bug reports already opened about it not working as intended on various large sites, including Facebook, Google Images etc.
It's pretty obvious to me that such sites are going to keep changing their parameters because they're privacy predators. If Mozilla is not willing or able to keep the parameter definitions up to date then this feature can end up doing more harm than good.
It's difficult to say what PP does, last I read about if? One idea was that it's actually excludes things from server side click metrics, and in that case I would guess I can see point in leaving it there?