Just a small glitch: if a post has staff color, it won’t onebox if the link is internal. They will onebox if the link is external, though.
https://meta.discourse.org/t/changing-the-color-of-staff-color-admin-customize-colors/27973/2
https://meta.discourse.org/t/changing-the-color-of-staff-color-admin-customize-colors/27973/3
Are you sure you’re not confusing external and internal links? Only external links will onebox.
Both of his examples are internal links, just to different posts. One being staff highlighted, the other not.
The other one is an invalid link, though.
Weird, it wasn’t when I looked at it a couple days ago…
Here is a different one (no onebox)
Non-Staff Colored Message
Let’s try this post which I made a staff reply
https://meta.discourse.org/t/basic-site-logos-should-hit-the-cdn/79306/5
Ah I see this is valid, indeed.
Yes, I linked to two consecutive posts in a topic which somebody seems to have deleted today. It existed 12 hours ago. If the topic didn’t, the first link i provided wouldn’t have oneboxed, either. 
Nothing critical, but at least it’s a known issue now.
@nbianca can you add this to your list? No rush, but staff colored posts should behave the same a any other public posts.