I tried to tag a question and found out that there are two tags which are somewhat similar: internet-connection and networking. In my opinion both are more or less duplicates and should be handled as such. What is your opinion about?
No, they aren't.
Networking clearly in-globes internet connections but and internet connection is a specific connection type used by millions around the world with a simple purpose. In fact it is so huge and largely scale used that people use it every day to describe: usage, problems, good time, actions, features, software, etc.
You don't go out saying: Hey, my new smart phone has networking connections_ or even _Hey my new smart phone has networking connections to other computers in a multi scale global network that allows me to connect via networking to other networking networks and allows me to open this kind of awesome services that work over networking connections.
You simply say: My new smart phone is connected to the internet and I can use the internet the all day to use many many services, unless the internet is borked.
So, no, don't merge the tags, they are useful they way they are.