Hi 00100001, hi everyone else,
Yup, it's as Sparklingbrook said, the fact of the matter is you've never been able to use MN smileys in thread titles.
We do see the problem with emojis showing up though. It looks a blooming mess, and we are going to sort this.
The trouble is, it's going to take our Tech team a while to fix, so it's looking like this won't happen until after Christmas now...