On Blurt you pay for upvotes.

On Blurt, you pay for all transactions.

There are two fees as you saw. One is a flat fee on every operation, and the other is a fee based on the size of the operation.

The formula is this:

total_fee = operations_flat_fee + per_kilobyte_fee * operation_size_in_kilobytes

I suppose this right here is a disincentive to spam.

That was the idea behind it.

In the beginning it was resource credits like on Steem and Hive, but we switched to fees instead during the first hardfork to curb the spam problem.

Fees are set by the witnesses. We each vote for what we want the fees to be, and the actual fees are the median of the witness-voted fees.

You can see the fees set by the different witnesses on this explorer: https://ecosynthesizer.com/blurt/witnesses