With all the awful wrongness in those paragraphs, the partner/lover element shouldn't be needed as a red light at all.

Heehee, true. But those are the stories where I find partner/lover most grates on my nerves. Because the entire fic is rife with bad writing and cheap shortcuts, and partner/lover as a constant epithet is one of those shortcuts. On the other hand, I have a list of words I just can't stand, but I find I am much more willing to overlook them (and in some cases, not even notice them being used) in well-written stories.

So it really does come down to good writing. But doesn't everything? :)