A general rule, but as with most things in software, there are exceptions:

Is Manual Modification of the Data Directory Ever Justified?

Sadly, I can’t answer “no” to this question. There are circumstances under which there is no reasonable alternative.

I’m definitely guilty of this and have mucked things up in the past (in dev, not prod!).

I still manually delete postmaster.pid a few times a month as Postgres doesn’t shut down completely sometimes when I reboot my computer. That file doesn’t get cleaned up, which results in Postgres not launching after the reboot.