dadepo: 

I'm pretty sure Bitswap can cancel WANTs so that it doesn't receive a block it has already received (e.g. I asked Alice and Bob for X. Alice gave it to me, so I send a cancel to Bob so that I don't get X a second time). If you're thinking about deny lists (e.g. I download a DAG starting at X, but it points eventually to Y, which is a block I know is bad, and therefore want to screen out the Y block) then that's not implemented natively in go-ipfs (maybe you're thinking of something like this https://github.com/ipfs/notes/issues/284).

For groups that run gateways you can always block certain URLs which would prevent you from loading certain content. e.g. Cloudflare could just block https://cloudflare-ipfs.com/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/ and then that page would not render on their gateway (you could of course download it on your own node though).

> I am doing a survey of IPFS for a school assignment so basically need to understand as much as possible of the moving parts

Cool, well feel free to ask questions people here are generally pretty helpful and responsive.