dba_afish said:
okay, going back and double checking this now, I am seeing what appears to be it rounding down like what you described, but not to nearest whole pixel, but to the lowest adjacent half-pixel, a floor function (so .33px rounds to 0, .66px rounds to .5px, and -.33px rounds to -.5px).

that behavior would actually explain what I was seeing in my screenshots. the drop shadows are all offset slightly to the top left, because all of the values I used were floored, half to 0, half to -.5px.

(body[data-th-main="<theme>"] makes testing these little things across browsers much easier.)

And I got the round towards 0 problem. Yay.