miners signal for SegWit2x or any other proposal in future not users.
and they should do it with a version bit in the blocks they mine. this process is done with a BIP which makes that version unique to that proposal so everyone can follow it.
for this particular proposal which is also known as New York Agreement they have been doing a different thing. they add a little text in their coinbase transaction saying "NYA". that is kind of an unofficial support.
you can see these things better here:
https://coin.dance/blocks#blockDetailsas for nodes, here is the client they have released:
https://github.com/btc1/bitcoin
