Thanks to Philippe for the addition of technical arguments in favour of a new code point. This is... a little beyond me. (Though fascinating reading!) I would particularly like to add me +1 to the knock-on effect this would have on downstream vendors. (I would like to see this become a standard emoji, and I'd like us to take whatever action increases the chances of that.)
I did just want to respond to the "slippery slope" comment. Firstly to note that this is the name of a logical fallacy :) and that it is a fallacy because it presume that people are unable to make reasonable judgements calls. As it happens, the Consortium appears to have mechanisms in place precisely to handle this sort of thing. When I mentioned my email to a queer friend, they asked if I might propose other pride flags (as there are many). As I pointed out to them, I would be happy to do so, should I be able to justify their inclusion in accordance with Annex C. (As it stands, I am not sure any of them receive wide enough applicable use for that, though perhaps there is evidence to the contrary)