Few times per day we receive new tickets which are created out of response to already existing ticket. We have to merge those with their original sources. The issue lays within HTML tags, what we have discovered in a following way:
We append a new email to an existing ticket by looking out for the Ticket ID in the response or header. We wouldn't differentiate between plain text or an HTML.
I will create this topic to a support Ticket and will have this analyzed and addressed immediately.