By most definitions of the word on-topic? You didn't.
1. If someone posts something, it isn't necessary to respond with "k". It is assumed that you read it if you are posting in this thread. If all you have to say is "k", then you don't need to make that post.
2. You made a pointless and negative comment about someone else's signature, which is most definitely not on topic. If you don't care for something, just don't say anything. Responding with a flat "Nope" is both condescending and also completely lacking in content. It doesn't even give a good reason why you disapprove of whatever they posted, which is why it is not an acceptable post. Saying just "No" or "Nope" to a post is not a good enough response.
3. Again, in reference to the title of the thread . . . if your only response to the entire thread is "Nope" then you don't need to be posting in it. You are basically posting to let the thread know you are refusing to participate in the thread . . . except you proceeded to spam four posts in the past seven posts, so you are simultaneously not contributing to the thread and filling it up with meaningless content.
4. The dirt block/platinum comment is also not necessary . . . we all know you didn't spend a ton of platinum to get a block of dirt. If that was the only post you made, it probably wouldn't have been an issue, but combined with all the other lack of content posts you made, it only contributes to the problem.
Those are some good guidelines for staying on topic and having posts with content in the future.