From the point of view of Unicode, it is simpler: If the character is in use or have had use, it should be included somehow.That bar, to me, seems too low. Many things are only used briefly or in a private context that doesn't really require encoding.
The term "use" clearly should be understood as "used in active public interchange".
From that point on, its gets tricky. Generally, in order to standardize something presupposes a community with shared, active conventions of usage. However, sometimes, what the community would like is to represent faithfully somebody's private convention, or some convention that's fallen out of use.
Such scenarios may require exceptions to the general statement,
but the distinction between truly ephemeral use and use that,
while limited in time, should be digitally archivable in plain
text is and always should be a matter of judgment.
The hieroglyphs discussion is interesting because it presents them as living (in at least some sense) even though they're a historical script. Apparently modern Egyptologists are coopting them for their own needs. There are lots of emoji for professional fields. In this case since hieroglyphs are pictorial, it seems they've blurred the lines between the script and emoji. Given their field, I'd probably do the same thing.
Focusing on the community of scholars (and any other current
users) rather than the historical community of original users
seems rather the appropriate thing to do. Whenever a modern
community uses a historic script, new conventions will emerge.
These may even include conventions around transcribing existing
documents (because the historic communities had no conventions
around digitizing their canon).
I'm not opposed to the character if Egyptologists use it amongst themselves, though it does make me wonder if it belongs in this set? Are there other "modern" hieroglyphs? (Other than the errors, etc mentioned earlier, but rather glyphs that have been invented for modern use).
I think the proposed location is totally fine. Trying to fine-tune a judgement about characters by placing them in specific way is a fools game. If needed, distinctions can be expressed via character properties.
A./
-Shawn
