Steps to reproduce

1. Create a page with title "something áéőü" (or any accented title)
2. Rebuild content index to be sure it will be present in the search bar
3. Create another page and create a link to this page by entering the page title of the accented page previously created, save the link
4. Edit the link, all accented characters will be converted to HTML entities

Workaround
Tested under 4.3.5, where the problem is not present anymore.