[wk_end]

So, this morning I happened to be reading a crossword blog - written by an English professor - and, reflecting on this conversation, thought, "Jeez, I'll bet Rex Parker uses the -y construct." So I scrolled back a few pages in his archives, and sure enough, earlier this month he described something as "bro-y" [0].

In case you still feel like you're more of an authority on whether this is acceptable in colloquial English than me (a Canadian native Engish speaker), OP (who - I peeked at their profile - appears to be a British native English speaker), or an American professor of English:

I also noticed, while scrolling through Rex's archives, that the Times itself had used the "-y" in the crossword. See the cited clue on 36A on June 18 [1], which describes something as "sting-y" - not to be confused with "stingy". Good enough for The Gray Lady, good enough for me.

At this point, I think - if it's still causing you to struggle with reading comprehension - you need to accept that it's a construct in common usage and spend some time practicing until you start to feel comfortable with it. Sorry, I know it's inconsistent; English is known for having quite a few quirks that you just need to get used to.

[0] https://rexwordpuzzle.blogspot.com/2024/06/strong-as-ox-in-s...

[1] https://rexwordpuzzle.blogspot.com/2024/06/extremely-damaged...

[Gormo]

As I mentioned in another comment, I think using the hyphen to eliminate ambiguity where it would otherwise create a word form that's easily confused with, or sounds like, another word entirely is perfectly reasonable. The "sting-y" and "bro-y" examples seem consistent with this, but "morph-y" doesn't quite.