Is there a pinning service that supports arbitrary IPLD?

Ideally one that has a good API that allows users to grant access to third party applications.

My specific use case is an in-browser IPLD editor that is itself hosted on IPFS (so no backend server that can store user IPLD objects).

You can upload car files to web3.storage directly: HTTP API | Web3.Storage | Web3.Storage Documentation

Thanks for the link!

How is web3.storage funded?

Seems too good to be true to be free with such a large data cap.

web3.storage is sponsorised by protocol labs.
The Filecoin storage is actually free because it’s paid with Fil+ (a validation power bonus for deals storing real verified data, and that validation power bonus is so strong that storage providers accepts deals for free).