A data processing system, including non-volatile memory storing a plurality of messages included in a group discussion among a plurality of users. The non-volatile memory may further store metadata including an ordering of the messages. The data processing system may further include a processor configured to, for a first message storage data structure and a second message storage data structure, each associated with a first user of the plurality of users, determine that the one or more messages of the first message storage data structure and the second message storage data structure are contiguous in the ordering. The processor may generate a merged message storage data structure including each message included in the first message storage data structure and the second message storage data structure. The processor may generate a receipt based on the merged message storage data structure and transmit the receipt to a second user.