Odd. I wonder if this is an add-on conflict or whatever but I tried adding the following into extra and the radius would not go. I even added important and still the radius remained it was only when I went into style properties and set the 5px to 0 that the radius was removed.
The background colour in the following code worked, but for some reason the radius would not change.
Code:
.nodeList .categoryStrip {
border-radius: none !important;
background: none green !important;
}
Probably best going into
Style Properties >>
Forum / Node List >>
Category Strip and just setting the radius field value to 0 if it's not changing through EXTRA.CSS.
Odd though because it should work through EXTRA.CSS first time I've encountered this issue.