I did find this comment because I too was wondering about this maximum capacity, what it was, why it was, and doing some research. I came here by google search on the very topic.
But it seems to me that in a world of automated script generated posts, there could be significant bloat on the blockchain if we allow any robot to post infinitely long posts.
Just an idea I had while doing this research. Happy to see you are still active!
I'm constantly checking SteemIt but as you've already specified the notion of "the more bots the more exposure" is just absurd and harmful to the ecosystem of SteemIt in the long run. Just check some of my posts, please. They are informative and rich. And then, check their earnings. You'll see that their earnings are so low other than some exceptions. This should be a platform where "the content" matters, not some "tricks". Absurd.