Based on the man page’s description, I’m inclined to think so. However, a good way to test it out is to just use pacman’s “dry run” feature, which will print out a list of packages to be removed without actually removing anything.
$ pacman -Rc <targets> --print
There is also -Rsu to remove unneeded packages only, to avoid breaking any dependencies. Hard to tell what command to use in what situation really…
provided that (A) they are not required by other packages; and (B) they were not explicitly installed by the user.
(c) man pacman
Which is exactly what you need, why would you need optional dependency that is unused by anything else…unless you’ve installed it explicitly (which means you really actually need it to be installed on your system, by mutual consent)
Ahh…what do you mean “why would I need it?”
Lets say you have two media players that share some common library as an optional dependency for playing a certain format. When I remove one of those players, I don’t want the other media player to use the ability to play that format.
Likewise, I don’t go searching my system to find packages like that and change them to explicitly installed.
Said differently, why would I ever want removing a package to remove the optional dependencies of a different package?
I do…that’s what explicitly installed packages are there for… 
If you really want something to stay on your system - install it explicitly.
Debloat, because it’s likely something that is unused.
2 media players example is great, i think.
If you need some library - mark it as explicit.
But i don’t know…maybe it’s just me.
During updating, got /etc/pam.d/kde.pacnew
Searching doesn’t help much - is it Ok to just remove it?
No, move changes from left to right, save it.
Putting aside the fact that find all those deps to mark as explicit would be painful process, I actively don’t want that.
If I mark it as explicitly installed, and later it becomes unneeded, then it will stay on system forever even though I don’t need it anymore. That method actually results in more bloat which I want to avoid.
Also, I mentioned this before but -Rs isn’t an alternative to -Rc, those two solve totally different problems.
That is interesting, you must have modified that file at some point.
What do i hear…you actively don’t want to know your system?! 
Hm, I definitely haven’t done it explicitly. And after quite a bit of searching, was able to find only this:
https://bbs.archlinux.org/viewtopic.php?id=293511
Will backup original file and try to merge as suggested 
I also had it both in clean VM and real system…never changed it.
If you are using yay use this instead:
yay -Yc
Or if you are using paru:
paru -c
I have marked many optional dependencies (libs and common, etc …) as non-explicitly installed.
# pacman -D <optional dependency> --asdeps
They remain when used by any packages. If no package use them, they are removed by pacman -Rns $(pacman -Qdtq).
I feel like we are going in circles and now we are back at the beginning.
The problem with that approach is that it removes optional dependencies of other packages. If that doesn’t both you, there is no problem.
ah yea always forget about yay 
i use aliases to have more control … and also to have meaningful names… i set unused to that option…
I’ve got this as well - any news on what you did and what happened next?
Merged changes from .pacnew, rebooted and so far so good.
Thanks. Good to know. Hope things keep rolling at your end.
Did you actually merge? Or did you replace?