Why is `pg_trigger_depth() = 0` bad to use (for anything other than debugging) when preventing trigger cascading (recursion)?

Can someone provide code to demonstrate why it is bad?

I am guessing because if multiple triggers are working on the same data at the same time a condition that stops a trigger using `pg_trigger_depth() = 0` will stop any trigger that is second in line to do work.

I thought it would be a good solution to this (my) question here, but I am told otherwise:

* [Within a trigger is there a way to tell if an update or insert came from a trigger or not?](https://dba.stackexchange.com/questions/163067/postgresql-within-a-trigger-is-there-a-way-to-tell-if-an-update-or-insert-came/163086#163086)

Thought it would make a good question.

It is offered here as a solution:

* [Prevent recursive trigger in PostgreSQL](https://stackoverflow.com/questions/708562/prevent-recursive-trigger-in-postgresql)

Postgres 9.3 documentation:

<https://www.postgresql.org/docs/9.3/static/functions-info.html>