Aggregation Pipeline for event sourcing

I am creating a database for a support forum (school project), with event sourcing. Objects stored in the database are question_posted, question_commented, comment_rated, etc. comment_rated can up-vote and down-vote a comment (+1/-1). For the display of the current state I set up a view with an aggregation pipeline. It works, but I wonder wether there is a shorter solution to this.
The example events are here: forum_events
My Aggregation is here: aggregation_pipeline