Taniguchi appears to have a 6th finger... o_O;

That's what the error tag is for. :)

Ugh, bad_art.

There should be a 6_fingers tag as well.

I tagged a few images with "extra_digit" but it looks like there aren't as many floating around as I thought - at least not within the "error" tag, anyway. To be honest I don't think it's really necessary.

The art isn't super but the guy is really funny. I don't know how he missed this finger thing though.

The author may have done this on purpose. He mentions the six finger thing on the page. Additionally, the picture after this one also has Taniguchi with 6 fingers.

あと…
谷口の右手指は６本。
これは公式設定だから外せない。

あと…
谷口の右手指は６本。
これは公式設定だから外せない。

"And... Taniguchi's right hand has six fingers. This was officially established, so there's nothing wrong with it."

Does he mean that Taniguchi's original character design has 6 fingers? If so, this doesn't even merit an error tag.

I think Kanno Takanori is basing her work off this video:
http://www.nicovideo.jp/watch/sm2416947
The very last frame of the video shows Taniguchi with 6 fingers. See post #222553

In fact, the lead-in page to the Shumi No Heya comics has a link to this video: http://passionalgallery.cho-chin.com/syuminoheya-iriguti.html

I can't see the videos. The first one requires me to join a website that I am incapable of joining due to not being able to read Japanese. The other video is a broken link.