When editing certain pages or macros on a page in Confluence, we semi-regularly are presented with a strange  character on the page.
A really easy way to reproduce this is:
- Add an Expand macro to the page.
- Add an empty table inside of the Expand macro.
- Edit the Expand macro - change its Title, for instance, then click Save in the macro editor.
After those three steps, each empty cell inside the table of the Expand macro body is now filled with that  character.
I've come across a few similar questions on the matter and some point to URL rewriting as the issue. We're not employing any URL rewriting on our external facing web server, so that doesn't seem to be the issue in our case.
We just upgraded to version 5.5, but have been seeing this issue since at least version 5.0.3.
Let me know if more information would be helpful.
Thanks!