Grammatically, I think ‘of’ can take either a noun or an adjective. The problem is that ‘this side of patience’ doesn’t make sense in a literal way. Readers have to construct ‘patience’ as a metaphorical place with sides, and put ‘a look’ (which is already being used metaphorically with ‘gave’) somewhere in relation to it. Try drawing a diagram of the look and the patience together and I think you will see the problem.
If you use ‘patient’ then readers will easily tie it back to the ‘look’, as in ‘a patient (or not-so-patient) look’.
I think I would say ‘barely patient’ or something like that.
Your editor is correct, for the reasons stated by the people actually answering your question. One means of determining what is grammatical is to remove the extra words that cause confusion. “Look that was patient” works, “look that was patience” does not. Your examples using other nouns would also not work.
Furthermore, the idiom is rather common and is perfectly understandable. There’s no need to know which side of the line you mean, since there is no actual hard line. What one person would describe as “barely patient” another could describe as “slightly impatient.” The difference is emphasis.
I think it is unlikely that there would be any confusion in context.
Concur. ‘Just this side of impatience’ /impatient might make sense, but it doesnt flow so well.
‘Just this side of patient’ means the person was about to be tipped into the state of being patient, but I think the OP is looking for the opposite meaning. Maybe ‘just the other side of…’
You are confusing grammar and semantics here. Or maybe grammar and style. But there is nothing grammatically incorrect about ‘a <noun phrase> that was <noun phrase>’.
a look that was the last straw
or a quality that was patience
I’m guessing that’s why Zuzu still kinda feels like her sentence might be right. It kind of is, in a way. It’s just a little hard to make sense out of, though you can get the gist.
I see your sense, but will suggest that it can be expressed more clearly. To me “just this side of” is hard to parse here. My first thought was what side of patience is this side? But usually “just this side of X” means “not actually X, but close to it,” whereas your stated meaning is “technically X, but just barely.”
The way what you’ve explained above comes to my mind is “'He gave me a look that was just barely within the realm of patience.”