On 7 Dec 2018, at 15:45, feek wrote:

in the find window on macOS 10.13.6 using TM 2.0-rc.22 a black border

I switched to having the scroll view draw the border, that should make it adapt better to whatever OS TextMate is runninger under.

Are other table/list views not using a black border (on 10.13)? E.g. Preferences → Variables.

What color is the bottom border?

It would be good to capture the entire window to assess whether this looks appropriate or not (for 10.13).