Dash and google reader

Found a very interesting thing. It turns out that if to use a dash "-" use # 151; , not mdash; , Google Reader (however, like GMail) will show □, and mail.ru - a question mark.
Under Windows, in Firefox 2, this symbol is skipped altogether, in Opera and Firefox 3 - □.
Under MacOS, Firefox 3 and Opera shows □, Safari comes in the same way as FF2 under Windows.