Metaphor: Treat each board as a beautiful polished floor and walking over it with an OT subject is like leaving footprints that everyone sees.
(I hesitate to write this post, but as your email isn't valid there is no other way to communicate with you, thus my request to fix the email in Personal Settings.)

Hmmm...an OT comment---

They're your boards, but I would suggest being a bit more comfortable with a bit more OT content, if the board participants are.
A different metaphor:
Each board is like a themed party or a bowling night. Everyone knows the theme, and follows it to some extent, and has chosen to participate in its community.
But within each party there are quite a few different conversations and activities going on, not all of which involve the theme of the party.

A bit of diversity of topics can lead to some very interesting serendipity, if it's a reasonably pleasant community.
The problem with things being TOO much on topic is that the board can die: when there is nothing new to say there is nothing to read,
and if the number of boards is too large relative to the population each one feels a bit too dry and sparse and narrow in viewpoint.

Just a thought! Feel free to ignore.

I do however believe all off topic threads should start the subject line with "OT: ".

Jim