But does a node on a lonely notebook have any real world impact? Do actors who accept Bitcoin payments connect to random nodes?
If so, what prevents someone from running one million nodes on a single laptop and "encircle" such an actor? There is no proof of work involved in running a node, right? So what gives a node any meaning or voting rights?
Regarding the impact of a single node on the network, that node is a way that _you_ can vote on what bitcoin is. You could equally shut it down and vote by connecting through someone else's node, but then you'd be trusting that their node defines bitcoin the way you want to.
In other words, the people decide what bitcoin is, not individual nodes, but the nodes that people connect through define what they are voting for. If you want to be _sure_ that your vote isn't being misdirected, that what the node is reporting as bitcoin really is bitcoin then connect to the network through your own node.
As long as you work for Blockstream Inc. If not you have effectively no say.
(I work for Blockstream, and we have no current employees in the top 10 contributors for this release AFAICT)
Everyone gets a vote on what bitcoin is, but the definition of bitcoin that you vote for is that defined by the code running on the node you choose to connect to the network through.
Running your own node let's you speak for yourself. If you connect to someone else's node you're effectively saying "I vote for whatever they're voting for".
The two parties calling toilet roll "bitcoin", are not actually using the bitcoin network. They're using the "toilet roll" network and simply calling it bitcoin. Their transaction would not appear on my node, or the vast majority of any other bitcoin nodes and therefore it's not bitcoin by consensus.
If you don't run your own node, you're trusting that the node you're connecting to isn't actually running the "toilet roll" network and you didn't just sell your car for a 6 pack of Andrex. With Bitcoin you never have to trust - you are always able to (and encouraged to) verify, and this is what running your own node allows: verification, with no trust required.