Identifying puppets on a post can be easy by simply looking at the account's post count and date of creation. These things aren't easy to find from chat, and identifying puppets with Russian or other alphabet's letters can be a little harder.
Clicking on a name in chat will bring up your pm history with that account, but what if you have no pm history with that user? Easy. Go to the "open pm" search bar and type in the name of the person you suspect has been replaced with a hard to identify puppet. Because your keyboard types in english characters when you finish typing the entire account name, only the original will come up.
There a a whole lot of fake PalePeach, AliceInWonderland, Blanc, Chapo, and bleary accounts right now (probably more of other users as well) and in some of them I can't even tell which letter has been replaced.