There seems to be quite a serious bug with IE10 and the moodle text editor.
I have created a 40 second screencast demonstrating the two issues as they are on demo.moodle.net http://screencast.com/t/PztHMHEdg
To re-create the issues:
1) Using IE10: Go to a moodle site (I tested on demo.moodle.net & moodle.org)
2) Create a new forum post
3) Enter a couple of paragraphs of text (so the scroll bar appears), try inserting a link using the link button
result: The text area will scroll to the top of the page and not insert the link
4) Click the 'post to forum' button
result: you will be informed that the 'message' section is 'required' (acting as if it's empty) to fix you have to re-focus on it and then 'post to forum'