Even so, at least you have the chance to be aware of that; if I typed this sentence using emoji, its
impossible to know what it will appear as in 5 years, without seeing into the future.
this comment could be interpreted as a threat 50 years down the line, by the change of meaning over time, but any sane person understanding that history and context matter, with knowledge of how it would be interpreted today, would realize its not. But if we applied the same acceptance to text as we do with emoji, the whole thing could be changed such that in both this time, and 50 years from now, it would be interpreted as a threat. The same context argument could apply, but I'm also sure defenders of the change would also not see the need to maintain a log of how things have been changed, as I doubt they care about emoji changes today.
The words themselves aren't simply appearing differently; they're changing, right from under my feet. The only defense is that (afaik) the unicode assortium has not changed yet changed the naming for it (ie CRYING FACE EMOJI), but since no one in practice refers to that definition, its not a useful defense.
Thus, emoji in their current form are highly inappropriate as a medium of communication, except in the very limited use case of short-lived, impermanent, and same-implementation communications.
But since this constraint is not the intention of the unicode consortium, and this is not the intention of the groups/font-creators that support emoji, and this is not a limitation that the general user expects, then this is a very poor design.
Emojis have been accepted as intentionally corruptible communications, but no party involved actually realizes the implications of it. We don't change ascii (ignoring the latter 127 characters, which are open to any interpretation) except by accident and by intentional non-meaningful changes (changing fonts does not change the characters themselves, just their aesthetics [except I guess wingbats]), and everyone would throw a fit if they did, because the notion is absurd