Should live location sharing timeline events be allowed to be replied to?

From `EventTimelineItem::can_be_replied_to`:
> Live location sharing session (MSC3489) events are state events, not always displayed in a timeline, so can't be replied to.

I'm adding MSC3489 support for Fractal, and we use this function. However it's not clear to me why replies shouldn't be allowed here. Element Web *does* support replying to LLS timeline events:

If I do this in EW, it doesn't render well in EXA, but it's not broken either (it links back to the correct timeline item). So I'm curious why this was explicitly disallowed?

From a user perspective, it's inconsistent that they can reply to some location events (the static ones) but not others (live ones). For how we planned to render these things in Fractal, there wouldn't be a noticeable UI difference, as it doesn't seem necessary, but because of this it might make sense to add some UI differences. It'd be preferable if we didn't need to.

I'm inferring also that these events shouldn't be forwardable, as it's ([broken in EXA](https://github.com/element-hq/element-x-android/issues/7190) and not supported in EW. I'm not certain what forwarding would look like, so that probably makes sense. If forwarding isn't allowed however, does that preclude replying to it?

Start at EventTimelineItem::can_be_replied_to and read how MSC3489 live location sharing events are classified as state events. Compare the behavior described for Fractal, Element Web, and EXA, then determine the intended reply and forwarding policy; done requires a decided behavior and corresponding SDK coverage.

Written by the indexing model from the issue text.