This means, the amount of merits gets less over time. Example: User A send 5 merits to user B, who is now able to send 2.5 merit to user C, who is now able to send 1.25 merit to user D... and so on until zero merits are left.
As stated in the title, this is only a criticism in the hope of developping the system further. I really appreciate the new system since quality posts seem to be rare here.
Only if you read the complete post there carefully. There are merit sources who get some merits to spend per month. There is no shortage of merit points and changes are being made as well. For instance, the admin is adding more merit sources. I suggest you to read the responses in the official thread as well:
https://bitcointalk.org/index.php?topic=2818350.0