I'm one of the maintainers of the PSL. The decision of LE to adopt the list for rate-limiting caused an unexpected rush of submissions, that in most cases are either hard to validate, potentially risky in the long terms or hardly justifiable (like adding 25k domains as part of a single provider).
In general, we're afraid to introduce new domains whose the only intent is to bypass the current Let's Encrypt rate limiting. Not only that can cause a maintenance issue on our side (people requesting to be listed in the future, as soon as they realize the side effects of being listed), but it may potentially cause a disservice to Let's Encrypt since they are relying on the list to avoid a rush of new requests.
That said, commenting the ticket will not push the PR forward as we're currently discussing how to properly proceed, in the light of possible rate-limiting changes as mentioned by @josh, and the override form mentioned by @jcjones in this post.
We're also discussing internally a new validation process for the private domains submissions, as it's getting harder to validate the ownership of these submissions (especially the relationship between the main company identity and the requested suffixes).
We understand the desire to be able to get a free certificate using Let's Encrypt, but if the goal is just to get access to Let's Encrypt, it's probably better to wait for the override form. Of course, if the request still makes sense besides Let's Encrypt and the requestor is fully aware of the implications of being listed, then we'll be happy to add the domain(s) to the list (as soon as possible).