My apologies if this is old hat to everyone, but it is new to me.
I've always been a little bothered by "quoted quotes" in epubs - when you've got a character speaking, and he's quoting something else. Having a double quote followed immediately by a single quite looks pretty bad, to me; it looks like a triple quote in most epubs I've seen. Putting a space between the double quote and single quote also looks pretty bad to me.
It occurred to me on my drive home this morning that I could fix that with css.
Then use the following in my html:
It produces results like in the attached image in ADE (and similar results in my PRS650).
I haven't decided yet if I'm OCD enough to start doing this in all my books.