Why create the markov text server side? If the bots are running javascript just have their client generate it.
2. You need to send the data for the Markov chain generator to the client, along with the code. This is probably bigger than the response you'd be sending anyway. (And good luck getting a bot to cache JavaScript)
3. As the author said, each request uses microseconds of CPU and just over a megabyte of RAM. This isn't taxing for anyone.
Anyone crawling at scale would try to limit the per-request memory and CPU bounds, no? Surely you'd try to minimize resource contention at least a little bit?