The comment can be considered a meaningful contribution as well. Dialog is not only information but also flow enablers and/or facilitators.
The fact that (s)he expressed sympathy/approval might show that others think the same, which in itself if a tidbit, if not too small. But it can greatly help others to chime in and relate or expand.
If you block these expressions then you get a lecture/dissertation, chock full of info, but not a dialog within a community.
So the question is: what do you see HN to be: a knowledge repository or a place that allows technology-minded people to share and belong?
HN has always blocked these kinds of responses, just as how they block pun, joke and meme threads. Memes are arguably more indicative of a community as they are an in-group norm, but HN has a clear stand against them as they dilute the quality of the discussion.
If you block these expressions then you get a lecture/dissertation, chock full of info, but not a dialog within a community.
So the question is: what do you see HN to be: a knowledge repository or a place that allows technology-minded people to share and belong?