Some characters are converted to "?"

I have something similar – I’m using html entities such as  – that’s ampersand hash xe000 semicolon – when I write that into the html editor, switch to Visual and back, they’re converted to the encoded character. (Which is odd, since that’s unicode’s Private Use Area, shouldn’t have any symbols in it.)

The rendered webpage works as expected, so I don’t actually have a problem. But the usability of the html editor would be impaired for someone that needed to see the html entities.