OpenType Feature Request: Small/Petite Capitals (smcp/pcap).

[jmcwilliams403]

Small capitals (in an open-type sense, not an IPA/Unicode sense) would be the height of old-style numerals. Petite caps would always be x-height (more similar to IPA/Unicode small capitals).
Examples under smcp:
Noto Sans Mono:

Roboto Mono:

Keep in mind that their coverage here is not exhaustive, as they do not show examples of cyrillic/greek small capitals, and long s (ſ) should share a small capital form with round s (s).
Some SIL fonts like Doulos SIL, Charis SIL, Gentium Plus, etc. have some examples, but not all at once.

[be5invis]

There are just too many things to handle...
Mark as far future.

[jmcwilliams403]

A question though: How much coverage is smcp/pcap(/c2sc) supposed to have, as you mentioned the other fonts don't do it exhaustively?

There is no rule. Open-type feature utilization is entirely up to the font developers and is independent from Unicode.
Some fonts only do Latin script, some do only ASCII, some do Latin and Cyrillic but not Greek due to casing issues being challenging, and some go all-out and give every character with a canonical capital counterpart in Unicode its own small-capital form.

[jmcwilliams403]

This feature has been raised before in 1815 and that one got Needs Justification.

This one actually cites monospace/programming fonts.