I saw this message today:
... which makes me wonder if I care at all about CSS1. It appears to me that most of CSS3 is supported by IE9, which is the oldest version of IE that can access our website after we started blocking everything except TLS1.2. So I probably could ignore all CSS1 messages and probably most of 2.1 as well. (Is there anything between 1 and 2.1 that I can also ignore?)[605] The "border-bottom-right-radius" property is a CSS3 property but not a CSS1 or CSS 2.1 property. Some browsers (especially older ones) may not support this property, or may have only partial support for it, or may require a vendor prefix (like -moz- or -webkit-).
I know you also don't care about old IE for your website.
It'd be nice to have a checkbox to disable certain messages for old browsers. But I suspect you're going to tell me that disabling a certain message number will do the same thing.