So they check it exactly one dozen times per day? Your correction also doesn't seem valid. Perhaps they meant to write that "We check our mail dozens of time per day."
First impressions are very important; I too find copy errors an indication of an inadequate effort to communicate effectively. However, that doesn't validate a malicious attempt to bash the writer(s) when a simple correction would have sufficed.
Should have been 'times per day.' I made a typo and couldn't edit it; I don't know why HN isn't letting me do so.
Asides from that, why post a correction here? Only other HN readers are going to see it, which inherently means you aren't writing the comment in the hopes of them fixing it, but to show the error to other commenters. Perhaps malicious was the wrong term, but your comment certainly wasn't trying to help them improve their copy.
First impressions are very important; I too find copy errors an indication of an inadequate effort to communicate effectively. However, that doesn't validate a malicious attempt to bash the writer(s) when a simple correction would have sufficed.