Oh.
I use Feedly and it is showing 31 days of messages in the history for the Kitz forum. From what I can deduce it polls about hourly (unless you pay for a Pro option). That implies that my feed is effectively throttled and I will only receive about 5 messages an hour. Enough to look active but I literally do not know what I am missing.
That link explaining how to customize the RSS results is extremely useful. I will increase my limit but first I need to narrow my boards.
Thanks for the heads up @jelv