[Dylan16807]

32 bit specifically?

The most expansive Unicode has ever been was 31 bits, and UTF-8 is also capable of at most 31 bits.

[int_19h]

You're right, the docs just say "Unicode codepoints", and standard facilities like "\U..." or chr() will refuse anything above U+10FFFF. However I'm not sure that still holds true when third-party native modules are in the picture.