Oh, there’s a reason for the first one: it houses links to related topics! See the Umineko general topic for an example (and this post, now that I’ve linked it). It’s also where “Reply as Linked Topic” appears once you get the appropriate trust level.
(Having too wide text also hampers readability a fair bit; your eyes need to move in a way that makes it easy to lose track.)
Also, We have colored text already! Use it like:
[color=red]There are only 5 master keys.[/color]
(This is also in the FAQ).
I agree about the spoiler (and perhaps color) buttons though, it’s just a little difficult to add buttons there. Both the spoiler plugin and the color plugin are official, from the creators of Discourse themselves, so it’s a little strange that there aren’t…