A user reported this odd behavior and I was able to reproduce it:
If you view the HTML code in a browser and copy and paste the rendered line with emojis into SyntaxEdit, then place the insertion point at the beginning of the line and hold down the right cursor key, you can see strange behavior as the insertion point moves across the line. The strange behavior mostly includes spacing issues. If you use the mouse to place the cursor point at various places on the rendered line then you can experience strange "jumping around" issues.
Can this be fixed? Thank you.