IE8 has a textarea bug where it “moves” the text when editing or moving the arrow keys. I've been battling this bug since we were upgraded to IE8. Very happy to find the fix.
http://grantovich.net/posts/2009/06/that-weird-ie8-textarea-bug/
Compatibility mode fixes the problem but is not required for other pages on our server so I went with fixing the problem instead.
For the Wiki, it is a simple fix to lib/tpl/default/design.css from:
div.dokuwiki textarea.edit {
...
width: 100%;
}
to:
div.dokuwiki textarea.edit {
...
width: 700px;
min-width: 100%;
max-width: 100%;
}