Afaik topic titles are wchars in the index, and the rest is simply html. So probably a limitation of the CHM compiler and not of the format.
Unfortunately, there is not much that you can do about that.
OTOH html afaik requires " to be replaced by & quot; did you try that ?
P.s. the ampersand and quote must touch of course, but the forum software would then turn it into a "