Joshua,

It's my experience that Google disregards punctuation of that sort, however, I'd use both of them on the page.  I'd use "inches" in your written description of the product and the " in the technical spects of the product.

Mayank,

If, when you type in the URLs and the server give a response of 404 (page not found) then they will eventually drop out of the index.  You may also use your Google Webmater Tools Remove URL  tool (under the "Google Index" link) to request removal of the URLS.

It feels like you're paying to much attention to the grains of sand and not enough attention to the beach. Think at scale--do you really want to be editing everyone's comments for ever and ever?  How would your audience think about that? If you're audience is prone to misspelings and grammer errors (and whose isn't) so be it.  One comment is worth a few errors and google's not going to ding you for that.

Instead, think about how you can get more people who are going to make those errors to your site. Don't knock your audience if they're engaging with your content.

Don't think about Google "counting" the words on your page--it doesn't really care about how many words it contains. The thing about words is that when used well, they can give others a reason to comment or share or like it--and shares and comments beget more shares and comments.  A six word page with 50 comments is a whole lot better than a 2000 word page with none.  In answer to your question, the comments on a page do count towards to the pages's content but the fact that the page has visitor profiles that have commented on it is where the real value is.

Yes, I read that too.  I'm sure you noticed the part about

"Content Rich Sites Get More Links

People feel content is so valuable that they are willing to link to in-depth content more than they are willing to link to content that is short."

Don't confuse google liking links with google liking content.  Google likes links--the content...not as big of a big deal (for google).

Nick

Your 301 redirect will take place on the server level and your nofollow will take place on the page level. The server is going to redirect the bot to the new resource before it gets to the nofollow. As far as whether you can use a 301 to escape a penguin penalty is the subject of substantial debate but it's generally not thought so. Here's one of the most authoritative and interesting threads on that subject: Google 2.0 - How To Recover.