Why do threads have to be disrupted by off-topic posts, all by the same person diverting to the same subject?

Excuse me CD, was that post posted because of my contribution? well I apologise but it isn't OT because I quoted the question asked by spawnjohn in post 206, then answered it.

I think my post was quite relevant and the question as it is a thread on public forum, as far as I understand, is open to anyone who wishes to contribute to the topic being discussed.

My intention is to join in with the knowledge I have on the subject not to disrupt it in anyway. Unfortunately I have no control how the readers will view my posts, as long as I do not post with unkind remarks, disrespect and vulgarity and am friendly in the way I post I would have thought I am doing nothing wrong. I am all for decorum on a forum in the same way as any of our other decent posters.