Here is a patch to add some information about the systemd RemoveIPC issue to the documentation, sort of in the spirit of the OOM discussion nearby.
I wonder if I missed part of the discussions around this, so maybe my understanding of the cases where this occurs is wrong, but isn't it the case of pretty much all (or actually) all the packaged versions of postgresql out there (debian, redhat etc) that they do the right thing, as in that they create "postgres" as a system user?
I like the text in general, but if the above is true, then I think we should put a note at the beginning of it with something along the line (not using those words) of "if you have installed postgresql using packages, the packager should have taken care of this already"? So as not to scare people unnecessarily?