My KR's do that as well, but it seems to be lessening as they get older. It has to do with the thinness of the bloom stalk in relation to the size of the bloom. My younger ones do it when there's a good rain to soak the blooms, or a good wind to blow them down. During quiet and dry weather, no problems..they perk right up.

"I'd like to have an OG that doesn't get too large, doesn't have to be divided, and is non-invasive."

This is tough. A very slow grower like Miscanthus sinensis 'Gold Bar' might work, but even though it takes years to reach 4', it will still have to be divided eventually.

Frances, perhaps you would like pennisetum alopecuroides "moudry'. The foliage is only about20-24" high, and it gets really neat blackish fuzzy plumes, which is definitely 'different'!

'Moudry' self-seeds furiously in my climate. It even sprouts itself in the lawn. I got rid of my established plants, but I'm still pulling up volunteers.

This one needs good drainage , does not like wet feet.