Not directly via the CP.

However, it you want to live on the wild side...

Edit the file "editpost.tpl"

At around line 97 find...

Code
<input type="checkbox" value="1" id="markedit" name="markedit" checked="checked" class="form-checkbox" /><label for="markedit">{$lang.MARK_EDIT}</label>

Remove
Code
checked="checked"


Always make a copy of any files BEFORE doing any edits of them. That way if something blows up, you can revert back to the original.

Further, it is best to try any edits of your files on a test instance of your forums and verify it works before going live.