What's the difference between a nod and wink?

Interesting snippet in the FT (found through Newshound), which identifies the ambiguity of Sinn Fein as the real reason the press are picking up ‘unintended’ messages from the party.

In an elegant signoff he says:

It is difficult to share power with people when you do not know whether remarks such as “I really don’t think you should pass this bill” should be interpreted as useful political input or a threat to your kneecaps.