  The transition to Terahertz (THz) frequencies, providing an ultra-wide
bandwidth, is a key driver for future wireless communication networks. However,
the specific properties of the THz channel, such as severe path loss and
vulnerability to blockage, pose a significant challenge in balancing data rate
and reliability. This work considers reconfigurable intelligent surface
(RIS)-aided THz communication, where the effective exploitation of a strong,
but intermittent line-of-sight (LOS) path versus a reliable, yet weaker
RIS-path is studied. We introduce a mixed-criticality superposition coding
scheme that addresses this tradeoff from a data significance perspective. The
results show that the proposed scheme enables reliable transmission for a
portion of high-criticality data without significantly impacting the overall
achievable sum rate and queuing delay. Additionally, we gain insights into how
the LOS blockage probability and the channel gain of the RIS-link influence the
rate performance of our scheme.
