Where does the 33.33% threshold for selfish mining come from?

The discussion focuses on the performance issues related to the mempool and block relay within a specific network, attributing these challenges primarily to the inclusion of a significant number of transactions with less than 1 satoshi per byte (sat/vb) by miners in their blocks. This practice has had a noticeable impact on the network's efficiency, particularly affecting nodes that are running on default configurations or versions older than 29.1. The timing of these events suggests that the majority of both nodes and blocks were influenced during this period, leading to an expected and observable slowdown in the system's operations. This situation underscores the necessity for nodes to either adjust their default settings or ensure they are updated to the latest software version to mitigate such performance degradations.