I don't always down vote, but when I do I prefer to leave a comment.
I've probably down voted someone less than 20 times on HN, but when I do I like to leave a comment as to why. Its been the case where I've been down voted and wondered why.
His comment isn't a troll comment and looking at his past comments he seems to be reasonable, intelligent, and otherwise a productive member of HN. I wanted him to know why I downvoted him, and he can consider changing the post to offer more insight in which case he would attract more upvotes and would generally make HN a better place.
What makes my comment more productive is that I articulated why I down voted which is that it lacked any insight into the process and didn't contribute to the conversation.
I don't think he should feel obligated to deliver. But, I think comments should generally add to the conversation. If they don't, I tend to down vote them.
A post about software being released happens. I made a (small) contribution to that software and mention it. It's subjective as to whether or not I added to the conversation but it's certainly relevant. You've been slightly patronising a couple of times in the thread and, ironically, you've only succeeded in starting meta-conversation.
I agree the meta conversation is of a particularly low value, and it wasn't my intention. Unfortunately, it's towards the top too!
I went back and looked for were I was slightly patronizing and the only thing I could find was this line: "So, you had two of your photos chosen for this release or no? Is that rare?" Which I can see how that could be more than slightly patronizing if it was read in a way that I hadn't intended it to be.
What I was trying to say is that for a project as big as Ubuntu, having two photos chosen seems to be a big deal. I didn't realize this when I originally down voted you, and I just wanted clarity.
In any case it was never my intention to be patronizing, so I'm sorry for coming across that way.
Just so you don't feel like the whole world is against you (I have no idea if / how many downvotes you may be getting) -- just wanted to chime in that I approve of your behavior completely, as well as the reasons for which you choose to downvote.
Thank you for trying to keep up the quality of conversation here.