Limit chaining in non-equivalence scenario?

If a valid equivalence binding exists, it is not possible (by design) to create a chain of references, only a many-to-one mapping. If however there are no inverse subpackets, then it is possible to create a chain. It may be prudent to implement a limit on how many such references should be followed.

We should RECOMMEND that only one link in a non-equivalent chain is followed per invocation. We expect most real world use cases will only ever have one or two links in such a chain, and if a correspondent needs a second invocation to get to the current certificate this is a relatively minor price to pay for stability.