I believe this is now resolved by the series of changes attached to T12616. In particular, D17840 introduced Quicksand-aware state to changeset lists.

I think we're mostly in the clear, now. This stuff likely introduces some bugs beyond the (mostly minor) ones I'm aware of, but I think it's all correct enough in the substantial ways. I'm going to take a break for a bit; I may get back to it tonight and land everything or may wait until tomorrow.

All of the inline comment icons got mis-aligned slightly a while ago. This is particularly visible with "Reply", I think. Note that the tooltip is centered, but the icon is too low (I think?) and too far to the right.

Really need an icon for points.

I'm having a tough time picking pieces apart here so that the transition is gradual -- many of the remaining behaviors are highly connected to one another and hard to tease apart. Things feel fine up to D17846, but even D17859 breaks enough stuff that I don't feel great about it, and doesn't seem to have pushed me through things enough to emerge on the other side.

Just noting that this cat is perfect and DOES NOT need any design improvement:

Everyone loves Opportunities For Improvement!

This stuff is probably going to churn for a bit but I'm pretty sure I'll forget about that thing if I don't write it down somewhere.

In View Options → Collapse File, we get into this sort of oldschool state:

Just some notes for myself:

I'm thinking about resolving this by having three states instead:

This reproduces for me at HEAD:

The keyboard reticle probably has the same issue but we can figure that out later.

Oh, this actually is the inline reticle, not the keyboard reticle.

Oh, the highlight itself actually is a little off if the reply is threaded. We move the comment up a little bit to make it visually thread a little more cleanly, but the highlight doesn't get a corresponding offset.

I'm going to try putting this on top of everything and using pointer-events: none to fix all the attendant click/hover/select issues.

There are three different highlights at play here, visible in this screenshot:

On mobile, I'd probably just keep this element in a fixed position on the page

@chad, some design stuff I'm thinking for later on, about in case you have feedback/ideas/objections: