recent issues with live preview of UserCSS with invalid selectors #2183

I use Stylus to edit and live-preview my own user styles for Google Chrome.

Needing a quick way to disable styles when testing and debugging, I became partial to [] (empty attribute selector). While technically invalid, it's easy to type, supports nesting (unlike comments), guarantees no performance penalty against large and/or highly-dynamic DOMs (because it's invalid), seemed to work well enough even as a simple selector, and also seemed to have well-defined behavior within forgiving selector lists in W3C Selectors Level 4 (e.g. W3C acknowledges and Chrome affirms that [] y is invalid but that :is(x, [] y, z) still matches x and z). This had been working fine for me.

...well, until two recent changes to Stylus:

1. Previously, StyleLint had become the default validator and its default configuration would reject this. I had addressed this by adding "selector-no-invalid": null, to its JSON configuration.
2. Now, Stylus itself has begun rejecting this, even when validation is disabled. This first manifested as issue Cursor in editor jumps to errors making it near impossible to write anything #2153 but, even with that resolved, Stylus will not live-preview such "invalid" styles. (Interestingly, it only seems to affect UserCSS styles, not native Stylus styles.)

I'm curious if this is a known issue (I can't immediately find anything about it), whether it should be considered a defect in Stylus, and/or what I might do about it (aside from switching to /**/ and :not(*) and suchlike, or perhaps switching away from UserCSS).

Cheers!