Hi Mr Z. Here is the site of Italki Russians learning English. Good luck. http://www.italki.com/partners/1-English-Russian--200-0--0-0.htm

I think Cherry is right in that it is rather natural for people of the same nationality to be able to recognize each other. So, concerning this sort of psychic power, I am no exception either, although I certainly don't dare to describe the exact workings... (Other than that, I can 'detect' Germans to a degree as well. :) This, however, is entirely mistake-based; any German person with remotely good English skills would easily swim under my radar.)

Hello Mr.Z, It might be their pictures, you recognize your native faces or if you don't see their pictures then the way Russians speak and write English ( the most common mistakes they do in general in sentence structure and spelling for example). There must be something you notice about their style of writing, their general views ,even if unconsciously, that makes you recognize them as Russians. And yes a Russian knows a Russian with no negative' thief' connotations ;) I think this question is rather left to be answered by Russians:) I just wanted to comment, because what goes for 'Russians knowing Russians' probably could be applied to other nationalities.