I believe it was the "Nice attempt, but currently wrong." at the start of the comment. "Nice attempt" could imply that this should be thrown out in favor of another attempt to solve the problem.
The entire comment was patronizing. "Nice attempt" minimizes the effort involved and implies the author is a novice. "but currently wrong" categorizes the entire project as a failure because of a single bug. The followup "From my own experience writing a formatter" really drives the whole thing home.
Also, “currently wrong” is a really sweeping statement to make based on a single problem written in a fairly uncommon style. Yes, there are things which need to be fixed but that doesn't mean we have to be so dismissive of someone else's work which they've given away for free to the community.
