[biblio] escaped characters in biblatex

[Haines Brown]

I'm trying to get on top of biber's handling of unusual characters. I 
have found some guidance on line, but no complete or definitive 
discussion so far. Can anyone point me to a good reference?

For example, there seems to be a different policy for author fields, 
key fields and all other fields. I'm never certain what I must do in 
one field might not apply to others as well.

In all fields it seems that there are certain characters that must be 
escaped, such as \# and \=. However, these are mentioned as examples, 
and I've not been able to find a complete list. For example, I 
encounted a direction not to use an ampersand as in "Roman & 
Littlefield" for a publisher, but to escape the ampersand as in "Roman 
\& Littlefield" or replace the ampersant with "and". However, biber 
does not gag on the unescaped ampersand, and this leaves me uncertain.

It seems that the author field can not have accented characters, which 
must be escaped as in \`{o}. However, it does not always work. The 
guide I use is http://www.bibtex.org/SpecialSymbols/, but if taken 
literally is says that one needs to escape accented "o" characters, 
but not a or e or u. Is that guide complete in that some accented 
characters need escape but not others? Also, the guide does not 
entirely work. For example, it implies I should escape the vowels in 
the name Lászl\H{o} Mér\H{o} in this way, but the bibtexkey name then 
appears as "MerHo". But if I do it more conventionally as Mér\"{o}, it 
shows up properly as "Mero". Any reason why bibtexkeys can't have
accented characters or even Chinese characters?

Finally, it seems the bibtexkey field is even more restricted in that 
it can not have an apostrophe or accented characters. For example, the 
author "O'Grady" must be edited here to be "OGrady". It seems that 
there's no problem with an apostrophe in other fields, although the 
recomendation to escape the apostrophe did not say it referred only to 
the bibtexkey values. I don't know how to escape the apostrophe in the 
author field so that it generates a proper bibtexkey field without the 
accent.

I wish I understood the logic of all this. It seems biblatex 
accomodates accented characters, but certain accented characters must 
nevertheless be escaped for some reason. 

Haines Brown