This seems to be a recurring problem at multiple Discourse sites.
Anyone with a Blog topic gets stopped from time to time, until a follower comments to free them to proceed.
“Has there been any progress on the garden project?”
“Yes, but I couldn’t post until you asked!”
Perhaps a better solution, instead of a limit of 3 consecutive posts, make it a limit of 3 consecutive posts in a given day? Or 3 consecutive posts for a week?