<p><pre><code> But I certainly would like to see more top comments that agree with what
the poster said, or expands on their argument.
</code></pre>
There are plenty of those, but it's easy to mistake them for sceptical comments. Questions, side notes, alternate interpretations, etc. <i>are</i> expansions of an argument, into territory not covered by the original post.
When someone starts a comment with 'However ...' or 'I mostly agree, but ...', the remainder of the comment is usually supportive, constructive and littered with tidbits that add to understanding of the point under discussion. However, simply due to the way the argument starts, we view it is 'criticism', because it sets itself up as countering the article, due to the use of an 'inverting' word/phrase, like 'however' or 'but'. There's probably a word for those words and this effect in English, but I don't know it.