We started stripping out a bunch of character ranges a few years ago because people were using them to play Unicode games in HN titles and the idea here is plain text. But I'm not sure in that case. You could test it if you wanted.
I tried it and it works. U+FF0B gives a plus sign when used in an HN title. It's a fair bit wider than normal, so may look a little off but not as off as "and". Here's a line of 10 U+FF0B's and a line of 10 +'s for comparison:
