On wikitech there is a discussion of the relative merits of having UTF-8 and monstrosities (for editors) like "è" or ᏲᏁᎦ/ᎩᎢᏏ
It seems that you can search wikipedia for èh or something. This will not find you èh. As wiktionary has many monstrosities, it would be best to convert them to something legible again.
I have been carefull not to add these things to en:wiktionary after I became aware of this problem, but I do know that many of these exist. In order to prevent them getting new ones, I think the best way of preventing this is by converting all wiktionaries to UTF-8.
I am still hoping that nl:wiktionary may soon be converted to UTF-8; there are many words that we cannot add to our dictionary because of this backwardness.
Thanks, GerardMare many words that we cannot add to our dictionary
wiktionary-l@lists.wikimedia.org