Not really. Given that the article's argument was "The old method of localizing manga was flawed because X, Y, and Z", I don't consider Y to be a good supportin

Not really. Given that the article's argument was "The old method of localizing manga was flawed because X, Y, and Z", I don't consider Y to be a good supporting detail when it essentially boils down to, "Japan has an irrational hatred of left-handed people." One is germane to the discussion. "I'm disregarding your argument because don't think your username is very professional" isn't, unless the discussion were perhaps about lack of decorum in online discussions.