Personally, I take it on a case-by-case basis.
For example, Adelaide Rd in Somerville, MA was incorrectly placed in OpenStreetMap. I ran it, but the nodes aren’t credited because they are misplaced. So, I’ll do two things: (1) correct the street on OSM, and (2) manually mark it as completed. I can see someone else having a different approach, where the “right” thing to do is trespass into someone’s backyard to get the node. OK with me if you think that’s the way to use the site.
There are other cases (e.g. buildings at MIT) where there are nodes deeply indoors. So, I ran through those buildings. GPS won’t pick up that I completed that node. I think it is literally impossible to capture that node. I complete it manually. Again, I can see someone else saying, “well, leave it incomplete then”. OK by me.
I totally get your judgement that that is weak shit and makes you scream. I can live with that judgement. But I’ve never “manually completed a node without running it” (or at least made a couple attempts to get as damn close to it as I safely can).
Someone else might be more lax about it, and make me scream. I guess. But I don’t really care how other people use the site.