Hi Nick, I'm sorry about the trouble you are having. For the timeline view, we did some updates to simplify the view, instead of showing full comment threads in that view, we are only showing the comment that was added with a review.
For the issue you mentioned around not being able to open a thread if the file is not rendered, we are looking into support when you click on a comment in the timeline, uncollapsing the file and scrolling to the thread. Would that experience meet your needs?
We are also investigating how we can improve the UX of the experience overall and will hopefully have some more improvements coming soon.