This was very much in line with the topic of the discussion, and I had another replying to a user still on that topic. If you are picking out the last line suggesting that your topic title is misleading it will seem like your problem is with getting those suggestions at all and not with off topic replies.
Yes, this aspect has already been touched upon here:
Quite often an extrapolating answer is judged by some as off topic.
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Also often a thread consists of mitiple diaglouges on different elaborations of the OP, like two or more threads in one.
Conversation drifts and develops, this may not be the best thing to do, you may be discouraged from posting something interesting for fear of it deviating from the original article too much, although it may still be relevant in the context of the flow of discussion. In this case posting a new topic would risk losing momentum if they missed the new thread.
And strictly speaking I don't have a clear or fully constructive position on it myself.
I often write posts in exactly this way: generally staying within the topic, but also adding a few sentences about something that interests me, even if it doesn't really help to develop the main subject. I've never seen this explicitly prohibited on the forum, and I never considered it a problem. But your comment made me look at it from a different angle.
You are absolutely right: it would be incorrect to call your post off-topic, since overall it is clearly related to the discussion. At the same time, the last sentence encourages a shift away from the main topic - it invites a response. I'm judging this by myself: I did feel the urge to reply, but I chose not to, because I didn't want to go off-topic in a thread that is personally important to me, as I'm trying to better understand Polymarket.
I tried to understand what exactly made me initially perceive it as off-topic. And I realized that, as someone who writes posts, I wouldn't consider such messages off-topic at all (again, I use this approach myself quite often when I want to stay within the topic but also add something extra). But as a reader, there is no real difference for me: whether participants go off-topic in a separate post or in just one or two sentences within an otherwise on-topic post. From a reader's perspective, it still feels like something unnecessary that distracts from staying focused on the subject.