Thread panel feels too narrow by default

### Steps to reproduce

1. Engage with a thread

### Outcome

#### What did you expect?

I was expecting the panel to be out of the way, but still accessible.

#### What happened instead?

A few issues:

The panel itself is so narrow that the timestamp is right up against the message (in 12 hr mode enabled):

The autocomplete is tiny:

### Operating system

Windows 10

### Application version

Nightly (2021-03-17)

### How did you install the app?

The Internet

### Homeserver

t2l.io

### Will you send logs?

No