Review the Ignore user behaviour

### Your use case

_We need to review and discuss the solution before implementing anything but raising here as a placeholder._

When a user is ignored, you can still see their messages in the room preview in the room list and the thread summary preview
Also, their messages are completely hidden from the timeline (main and thread)

We should think of ways to protect users from those they have ignored (don't show message content) but also not confuse folks by hiding the message entirely.

Before making any code commits we should audit the current experience from lots of angles (I only did a little research to find these two examples, I'm sure there are others), consider the impacts, make design/product decision, and then fix :)

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

Audit ignored-user behavior across the room-list room preview, thread summary preview, main timeline, and thread timeline. Document the current experience from these surfaces, identify additional affected cases, and establish the product/design decision before defining implementation work.

Written by the indexing model from the issue text.