Interesting! Using the new Edge browser which comes with Windows 10 I had problems with the text editor on the Model Boats website. A bit of Googling suggested that this is because Edge doesn't support the 'compatibility view' settings in IE which enables older software designed for earlier versions of IE to be run properly.
So I have switched to IE in Windows 10 and when I try to put a smiley into a post on here it displays the characters rather than the smiley picture but shows the smiley properly in the preview so the following might just possibly look OK in the actual post itself:

Looking at the comparisons, I don't think I need the extra features provided by MS Edge anyway.
Colin
Edit: It worked!

Looks like the smiley issue is browser dependent when using Windows 10 then.