U+FE0E is really interesting, it forces monochrome emoji usage on the immediately preceded emoji (like a skin tone modifier or any other modifier). I have previously run into the issue of the play-pause characters (U+25B6, U+23F8) being inconsistently replaced with their color versions when I was trying to use them in a UI. It looks like this is a great guarantee that that won't happen.

Also is it seems hacker news automatically removes emoji, maybe this modifier would allow them to keep them (in b/w form) and still maintain the polished appearance.