When my pebble smart watch gets the Monzo notification the emoji displays as square.
This most likely because pebble only supports a subset of the emojis. Emojis like pizza or cash are not supported hence displayed as a square
Ah that makes sense then as I’m sure I’ve seen some displayed and some not!
Long standing issue with Pebble, they have incredibly poor unicode coverage. Main reason why I left Pebble for an Apple Watch, half my messages were in Japanese and that was completely unreadable on the watch. Even firmware hacks could only give you limited sets of characters.