Most email IMAP servers provide both Date Sent and Date Received properties for each message, allowing the client to sort by either. Even in active mailing list

Most email IMAP servers provide both Date Sent and Date Received properties for each message, allowing the client to sort by either. Even in active mailing list threads, I've found that it's not that common for messages to get too out of order. Assuming federated social services keep track of Date Received, it'd probably be okay to just sort by that.