Thanks for the response.
Since all upvotes result in a curation reward, the system need charge only one reward.
IMHO, the system should charge for manual activities.
BTW: I recorded my account value. Received several curation rewards. The value changed a little but not the recorded value of transactions.
Blurt does not have an RC system like on Hive or Steem and that is why every type of transaction has to be paid, otherwise dishonest people could set up hundreds of bots which would exploit the “hole” , this would overload all the nodes and collapse the blockchain