While not a canoe topic, I thought the original topic was somewhat relevant to discuss and wasn't going to post in it, but for some reason Johnny 5 has deleted his original post.
I took it that his main point was that drift in an informational topic that the OP has put a lot of thought or work into, such as a specific boat build or a DIY project (or even a trip report), should not be taken far off topic by a lot of drift. I think that's a legitimate point of view. There may be other legitimate points of view.
I've always felt that a thread starter has a sort of "right" to come into a thread and request folks to stay on his or her topic. As administrator, I don't think I'd get involved officially unless the drift was really egregious or ventured into an area against the rules, in which case I'd probably lock the thread. So far, that has never happened in my tenure.
Since Johnny 5 has withdrawn his original topic OP, there's probably not much constructive to be gained by further debating this issue in the abstract and possibly provoking each other, all of whom have been very valuable contributing members here.