`table-input` and `collapsible-content-button` don't appear on some review forms #4542

It seems this happens because the textarea and its associated toolbar don't exist on page load, they're first created when adding the review comment. Reloading the page makes this bug go away.
The same thing happens with resolved review threads since they're lazy-loaded.

Using the additional onNewComments listener fixes it for resolved threads but not for new review comments. Should the listener be extended to cover this, or should we rely on some kind of observer instead?

Also the upload button resurfaced by minimize-upload-bar is not showing

The button is missing, this seems to be a GitHub bug.

they're first created when adding the review comment

By who? Are they loaded together with the comment itself as a partial? Do you see any events that we can use in GitHub’s code? onNewComments seems unrelated (and as you mention it doesn't catch all cases) and selector-observer feels heavy, especially on a page that tends to get huge and already has trash performance on long PRs (especially on Safari)

We could potentially use onElementRemoval to track a submission and then look for the new form when that promise resolve, but this seem very fickle.