Comment # 3 on bug 1045898 from Wolfgang Bauer

Well, this problem seems to be a bit more "sophisticated".

On my 42.2 system here (with Plasma 5.10.2), $HOME/bin is in the PATH on my
normal user account, but it is indeed missing when I login to a certain other
account.
I also tried creating a fresh account, and $HOME/bin is in the PATH there too,
even after logging into Plasma5.

I still don't think that this is a KDE problem, because on the affected account
it is also missing if I login to IceWM (or if I run "su - username" in a
Konsole/xterm).
I added debug output to /etc/profile and that shows that it is actually added,
but it's still somehow missing after login.

I'll try to find out what triggers it, but it may take some time...

@Marco: can you please try whether a fresh account is affected on your system?