Comment # 13 on bug 900639 from Petr Gajdos

(In reply to Stanislav Brabec from comment #12)
> By the way, /usr/share/myspell is also a set of symlinks.
> 
> Shouldn't firefox link to /usr/share/hunspell?

Depends on what firefox needs from myspell-dictionaries.

You are correct, /usr/share/myspell is deprecated (all-in-one) location and
there is compat-link set nowdays. 

/usr/share/{hunspell,hyphen,mythes} are new locations.
hunspell: dictionaries
hyphen: hyph*.dic files
mythes: thesaurus files

Using new locations is of course prefered.