it has some positive effect on the suffering of animals (which I've said I'm skeptical of)

If going veg indeed has negative expected utility for you, my paraphrase indeed was a wrong strawman.

I guess I found this

It's not clear to me that my deciding to switch to a purely vegetarian diet would have the consequence of preventing the suffering or delaying the death of even one animal.

hard to accept. Here's the argument against it.