Thanks for raising this :D
You should be able to navigate through the options shown using the arrow keys on the keyboard, clicking onto the desired option (if on desktop) or by touching the desired option (if on mobile).

One question I do have is do you think it's clear enough which option is highlighted?

I'm focussing on the /first command here, but we need to ensure the scenarios work for all commands.

Some options around what we could do here;

1. We could change the names of the commands to group them better. e.g. /first /firstInThisChannel
2. We could change the ordering from alphabetical to a predefined order
3. We could get a bit fancier with the text matching - /fi should match "first" before "channelfirst"

My preference is 3 - even though it's more work than the others.

I personally think we need to adjust the opacity for non-highlighted options to like 50% to make it even more obvious which option is currently highlighted. White text vs "splash" colored text isn't enough context.

I disagree that this is not a bug. When you type /first it selects /channelfirst unless you manually select /first from the list. Typing /first should not send /channelfirst