We had a style difference early on but it was extreme, so we abandoned it. (I think the background color was changed; it’s been a long time.)
I think “bubble” is way too extreme. If anyone has ideas of minor styling things we could do to make PMs stand out more, post a screenshot.
I’m still in favor of a just-in-time education panel for your first non-discobot PM.
It would be useful to have more distinct styling in the email notifications too.
The ‘speech’ bubbles can be more subtle depending on styling. It’s the shape that helps signifies it a personal chat rather than a forum post. The colours are optional. It’s good to give users and administrators a range of options - the Discourse themes and components work well for that 
Shading
Borders
Ah maybe. Let’s see what @Johani and @awesomerobot and @jordan-vidrine think?
If we had speech bubbles we’d need to alternate sides, because that’s generally the standard on other apps… seems doable.
We do a lot when it comes to image resizing and ensuring there’s no page shift, among other embedded content types… so there’s a lot of potential overhead for an entirely different topic style.
This is a bit of a tangent and doesn’t make PMs any more discoverable though!
The different sides would also help distinguish PMs I like that 
Eh, I don’t view that (if we do bubbles, they must alternate sides) as a hard and fast rule, because it turns a light reskin into a giant layout problem. 
Why not try a very “light” version of speech bubbles with everything on the same side?
