Is there a way to count the number of transactions coming from noise.cash?
It is hardly. Noise.cash is actually a centralized censorable platform which provides an easy way to send BCH tips. Those txs are normal txs w/o OP_RET and impossible to distinguish.
Instead, there is no way to prevent you to send any content to memo.cash. Because you can directly record your content to BCH chain by using memo protocol.
