RE point 4, I believe that this was initially a descriptivist rather than prescriptivist step.
People were using emoticons, showing that emoji might be desirable. Some cell phone manufacturers/carriers added their own emoji [1]. They were very popular. Unicode added emoji to the standard, since lots of people were using it.
Not adding emoji would have been _more_ prescriptivist, and since it was desired anyway would have just caused fragmentation.
Not in the Unicode guidelines as they currently stand ':).
They are very explicit that this is not permitted [1].
Also, RE :poop:
1. Huffman encoding philosophy - encode frequently used symbols using fewer bytes.
2. Standards are helpful, :poop: is very English-centric, whereas U+1F4A9 is much more interpretable.
Did you know that eons ago, people would draw a picture of a bull to mean a bull? Then they got lazy, and would just draw the head? Then they decided to just have the bull's head represent the first sound of their word for bull. Then they simplified the bull's head to 3 straight lines (people get lazy). Then for some reason decided it was easier to write if they rotated it 180 degrees.
A
Yup. A bull's head. But now that's no good anymore, and we're back to a picture of a bull, and need about a million more pictures to flesh out our new and improved alphabet. (There are a million words in the English language.)
Considering the explosion in emoji alongside photo and video now that it's more accessible to the masses, one suspects that most people prize being able to communicate in more ways that might be informationally inefficient, as opposed to what you seem to prize more in being able communicate through text alone.
People were using emoticons, showing that emoji might be desirable. Some cell phone manufacturers/carriers added their own emoji [1]. They were very popular. Unicode added emoji to the standard, since lots of people were using it.
Not adding emoji would have been _more_ prescriptivist, and since it was desired anyway would have just caused fragmentation.
[1] https://blog.emojipedia.org/correcting-the-record-on-the-fir...