Is making eye contact and smiling appropriate behaviour for seeing someone in the hall who you don't wanna talk to?

I think so, that’s how I greet my neighbors. :)

It’s probably easier to smile and glance away quickly than to pointedly ignore someone.

A small smile, not a broad grin would be appropriate along with polite (not lingering) eye contact.

I greet people that way. It’s fine, as long as there isn’t too much sparkle.

You could always go with the “acknowledging nod”. Then you don’t have to worry about smiling.

A brief smile or nod will do. Just don’t throw in some jazz hands. ;~)

When you smile at someone, eye contact doesn’t have to be a factor and I don’t see it as an automatic invitation to engage in a conversation. You can look at their chin or over their head but it is the smile itself that will be remembered after the moment has passed.

I’m comfortable in giving smiles to others and I enjoy it when others take time to give me a smile. It just makes me feel good.

I give a slight nod and keep walking. If I really don’t want to talk, say if it’s someone I really don’t like but have to be civil to for whatever reason, I pull my phone out and start fiddling with it so my attention is off them.