Right, I wanted to mention that Telegram (which IMO offers the best UX among messengers) keeps the order of pinned chats.
WhatsApp Android and Desktop also don’t re-order chats based on activity. When you pin a chat, it goes to the very top of pinned chats and stays in place until you pin / unpin other chats. And there is no way to drag them.
Edit: Signal Android also doesn’t reorder pinned chats based on activity.
FYI I saw this algorithm in Vikunja.
Maybe it’d be simpler to just update the entire table, since there is not supposed to be a ton of pinned chats.