Handling tickets with customers' replies marked as internal comment

In Zendesk, if a customer replies from an e-mail that is not included in CC or not a requestor of a ticket, their reply will be marked as internal, and SLA will be reset. Such ticket can be left in the queue without attention for a long time. Current workaround is to add the user to CC and reply. After that their replies will not be marked as internal anymore.

This is default Zendesk behavior, see https://support.zendesk.com/hc/en-us/articles/203661606#topic_d32_mzc_3r. There is a number of threads about it at Zendesk forums:

• https://support.zendesk.com/hc/en-us/community/posts/360003009867-Reset-SLA-on-replies-from-third-parties-
• https://support.zendesk.com/hc/en-us/community/posts/115000991347-SLA-based-on-internal-notes
• https://support.zendesk.com/hc/en-us/community/posts/360004389367-Communicating-with-users-about-internal-comments-vs-public-comments-from-email-replies
• https://support.zendesk.com/hc/en-us/community/posts/360004375507-Ability-to-make-an-internal-comment-public
• https://support.zendesk.com/hc/en-us/community/posts/360000993288-Comments-by-users-not-explicitly-added-to-the-ticket-will-be-flagged

I have not found any good workaround for such behavior, and the current workaround is pretty inconvenient. @lisvinueza, do you have any ideas how we can deal with such cases better?