To DiapDealer about double unescaping.
It is not that innocent as it can appear.
Of course if value doesn't contain any '&' additional unsnapping would not do any harm.
The problem happens when unescaped value contains known entity. For example is title of the article is "Don't double unescape & in metadata".
Escaped string would be "Don't double unescape &amp; in metadata".
If you unescape it twice or unescape original string you would get "Don't double unescape & in metadata" and this is not what original title was.
In short: double unescaping is a bug and it results in "data loss".