Yeah, I will say that I downvoted you. Your expectations (source code, that the results would be documented to your satisfaction after a trial of size N=1) seem unreasonable to me, to the extent that I personally think it is downvote worthy. I don't think, "where's the source code," contributes to the site, especially in situations where one would not reasonably expect to have access to it.
----
I have definitely seen the pattern where something I say initially gets downvoted, or upvoted, then the reverse happens later. It seems at a minimum that there might be a difference between the populations of people who read a story soon after it's posted and long after it's posted. It wouldn't surprise me if different sorts of comments appeal to these different groups, and that's ignoring the content of replies.
Personally I would suggest not worrying about it too much, and doing your best to make comments that seem good to you. For a long time, I actually had a userscript that eliminated the fading style that gets applied to comments, and also hid karma and points. In some ways, that makes using the site a little less stressful, because you can worry a bit less about what others think.
Edit: this comment is a good example of one that initially received several upvotes, but is now negative. ;)