Is it possible to read/write software reviews in different languages?

You can logout, choose your own user again, but on the bottom of the screen set another language to use, it will change the prefered language when the Software Center look for revisions, but you may notice that the whole system will use that dictionary and to get back to your default language you will need to logout again and change that language.

Summarising, it's still a lacking feature and logging out and in isn't the most convenient way to read revisions in other languages. Hope they'll include this feature in Oneiric's Software Center!

Maybe you can launch it from a terminal with

LC_ALL=lang software-center

That way, everything should be set to a different locale.