The patch to r101052
Now, wikilog just shows an error page on session failures when posting a comment.
In some "browsers" (if MSIE is really a browser) user loses his comment text, because these "browsers" do not preserve it on clicking "Back".
I think it should be solved by displaying comment preview instead of an error in the case of session failure.
The patch is attached - it's pretty simple, but maybe I'm wrong somewhere again? :)