@nax The root cause of that is ipfs-http-client does DAG traversal on the client side, and on every traversal step plus one event listener gets added to one long-lived AbortSignal.
Say, if you do ipfs.dag.get(cid, '/some/long/path/like/for/anchoring/root'), every element of the /some/long/path/... results in adding an event listener. After a certain number of listeners, Node.js starts complaining.
To be clear, we do not expect the issue to affect Ceramic node production in any significant way. Consider it an annoyance.
The path is to (1) provide a capability to remove the listeners, which is done in the PR mentioned above by @avi , (2) use the removal capability in js-ipfs-utils package which does the actual work. And, the second part is not quite fun, as the package has been neglected for a while (not by Ceramic folks; it is an internal dependency of our internal dependency).