In debugging mysql problems, mysql developers often request a user to "resolve the stack" from the mysqld.err file. This requires a symbol file or symbols in mysqld. The precompiled version of mysql ships with such a file. Currently the only way to get symbols in mysql is to compile with FEATURES="nostrip" which has to be done before the fact, and would invalidate any existing stack from mysqld.err. It would be handy to have the mysql ebuild generate a mysqld.sym file before symbols are stripped and put it someplace like /usr/share/mysqld that a user could use to resolve the stack.
FEATURES="nostrip" is needed for any debugging, don't really see why mysql should have special of stripping.