both.
only issue with the feature is that if you're at the bottom and you want to "pin" someone, you get scrolled all the way back to the top. ditto/opposite for "bury".
Discussion
Well, the best UX here is quite subjective, seeing the result of the action (with the scrolling) VS letting the user go on an pick other profiles. I need to evaluate.
For sure I dislike the fact that when you unpin/unbury someone, the scrolling follow the profile, this makes no sense, I need to fix it.
a "sent to top" toast could do it.
users get past the 'feature learning' phase pretty quick and enter 'efficiency from here on out' permanently.
I don't like when an application is too verbose about what it is doing during the interaction, it usually is a red flag about usability. Then toasts notifications opens a lot UX issue (how to stack them, auto-close o explicit button, etc).
Maybe the row could simply change is aspect and present the "sent to top" info.
Anyway, as you mentioned later, users should quickly learn how it works, and after a while they will no longer pay much attention to these details.