Mainland traders will have a nasty shock on their hands when they return to their computer screens on Thursday after a long holiday. The Hong Kong market saw heavy selling here on Wednesday in Chinese tech names such as Alibaba Group Holding ( ( BABA ) and HK:9988), which dropped 3.7% on the day. Investors were spooked by just about anything. They were spooked for a second when they thought Alibaba lightning rod Jack Ma had been arrested for publishing seditious stuff on the Internet. That wasn’t true, but it was pretty funny. Investors also were spooked by ride-hailing operator…