Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

Here's the scary sounding part that can be counterintuitive. The routers you're communicating with do know your ip, since they have to like you mentioned. Your ip address is also in i2p's DHT as a "router info" which functions as a network addressbook for routers and services so things can be found without needing a centralized lookup service. Again, because for the network to work, routers need to be able to find eachother, or they can't communicate.

But, routers function on a need to know basis. i2p uses separate up and down links for each tunnel, and your side of the tunnel by default has 3 hops. other side usually also has 3 hops. typical unidirectional tunnel looks like this with total of 7 hops:

A-x-x-x=x-x-x-B

None of the chains in the link know what position they're in (except for the endpoints). They also don't know how long the whole tunnel is. The sender and receiver only know their parts of the tunnel. On the dht side, by design no single router has a whole view of the network, but there isn't a whole lot of information you get from that other than knowing that person at stated ip address uses i2p, which your isp would be able to tell for example anyway just like using tor or a vpn. There's no reason to try to obfuscate that except for getting around restrictive countries firewalls.

The way i made sense of it was like you have an envelope that is inside several other envelopes, with each envelope representing a layer of encryption. You get an envelope from kevin, so you know kevin. You open the envelope and see another envelope addressed to george, you give the envelope to him. So you know kevin and george. But the rest is unknown to you. You don't know who the true originator of the envelope is or where the message is ultimately going.

Not a perfect analogy, but because of this the ultimate sender and receiver are blind to each others ip address. It's layered encryption allowing this to happen which is similar to onion routing. Called garlic routing in i2p since there are some tweaks.

https://geti2p.net/en/docs/how/garlic-routing

Unless there's a zero-day, no. All traffic is encrypted and it should be impossible to correlate traffic chunks to identities like that

No, since they don't act as exit nodes (they're called outproxies in I2P), unless you specifically configure that. It's like running a Tor middle/guard relay. I2P was specifically designed that way, so everyone can use I2P and be a node by default without causing any trouble.

After reading that whole page, I think your point is missing.. The use case of Tor and i2p isn't correctly explained on that site.