Some feedback on new CSS border radius and padding

I just updated Discourse to the latest version and there are some issues with new CSS border rounding, especially on sites with dark headers.

Here’s a screenshot from a dark header where the pieces don’t fit together cleanly any more:

A rounded border against a flat line doesn't look good

Here it is on this forum with a red CSS border added to make it clearer:

The same thing on this forum

Here’s what it looks like on a forum that wasn’t updated yet — I think this looks much better with less rounding and with the old padding (and no rounding where a corner touches a straight line).

I think the less rounded borders looked better overall. Here’s another example:

Here’s the old version for comparison (looks better in my opinion, though the outer corners might look better with a 2px radius):

Just some suggestions.