How does the bot associate the WoT of the sender to the report it files? 

A report from you should be more valid to your followers than a report from a spammer that has not follower. 

If that information is not in the Report, I am not sure what's the point of the system because anyone could just report anything they don't like and just hide behind the bot.

Meaning, people get to report and take posts down without being accountable to the public.