Code review comment for lp:~quam-plures-core/quam-plures/posting_xhtml-fixes

OT: you tinkered in an area I have a heavy tinker in, so it is going to kill me to make it be "mine" again. The html_sanity_check function is where I added a bit for one day going to xhtml(trans,strict) and/or html5. Such is life eh? Hopefully I'll be able to deal with it smartly later on :)