Can a Bitcoin node create an outgoing connection to a inbound node? I'm trying to figure out if we can create an outgoing connection to a inbound node (a node which we are already connected to, but the remote peer has initiated the connection). I know that this does not make much sense since we exchange information to inbound and outbound nodes. However, I have looked at the source code and did not find the code that prevents a node from doing that. Is anyone out there more successful?
Nothing prevents this as it is impossible to distinguish whether the node that is connecting to you is the same one that you are already connected to. This is because one machine can run multiple node software or multiple instances of the same software and thus it can be multiple nodes on the network.

There's also no reason to block such a connection.