I feel this is actually a set of really important questions that go right to the very heart of your site.
First things first, analyse what you have already and put to one side the question about SERPS:-
|...for 3 years where I post mostly web development related articles along with some other articles dealing with topics that interest me. |
Good start. I would bet that it's a pretty good site as you clearly write well, and you write about what you know and what interests you. That generally means good content.
|Recently I have been thinking about adding an option for readers to comment on the articles I write. |
To my mind the whole blogging phenomenon and "Web 2.0" scene has created this ethos that Community is King. While I do subscribe to that to a certain extent (for the most part that's what I do), I do feel that there's incredible value in non-community sites. Both have their place. If your articles naturally attract high quality comments, then moving toward a blog format (and as soon as you add comments it's basically a blog) could be a good thing. If comments are only likely to be praise and appreciation then they will add no value whatsoever to the reader. They would serve only to massage your ego (which is no bad thing necessarily, we all need a little love from time to time, but you can get that equally well by email).
|....or ask for help in implementing my ideas on their site. |
Have you considered whether a forum is a more appropriate vehicle to allow readers to discuss your content among themselves?
|1. Will adding comments at the bottom of each article make Google or other search engines change the ranking of the article because there is a bunch of new content? |
Possibly, yes. Could be for better or could be for worse. If the nature of the content (including word density etc) changes substantially, a change of some kind in search traffic for that page is highly likely. Could be for the better, could be for worse.
My thoughts about a forum are partly with this in mind. Rather than change existing pages, allow the commentary to take place in new ones. It's one option.
|2. Will adding comments water down the article and have a negative effect on keyword targeting? |
Possibly, yes. That's a similar question to (1) really.
|3. Would it be better to have the comments on the same page as the article or to have a link to the comments which would be displayed/added on a separate page? |
Again, that says to me "forum", not comments.
|4. For an article with the title 'How to Implement Widgets on Your Website' if the comments are done on a separate page what should the title of the comments page be? I was thinking 'Comments for How to Implement Widgets on Your Website' but is this too similar to the original article that it would cause a duplicate content penalty or some other problem? |
The content wouldn't be duplicated - only the title would be. And yes you could tailor that title with "comments on" or similar wording. As you have a tailored CMS, you could also set the title of the comments page manually at the time that you write the article. That gives a lot of scope for the basic SEO of what will become a new page. You could even elect to have some pages commentable, others not.
One thing to note is that you will require some kind of moderation engine for comments. Personally, I would have all comments pre-moderated and you'd need to get into a daily routine of managing that moderation.
Forums of course require a lot more work. That said, if you have a bunch of users that clearly like to engage with you and with the content that you create, you could have a sound basis for one.
In terms of SERPS and the original question behind this thread, I would suggest that the safest bet is to have the comments on a new page. That will protect the existing content pages to a sufficient extent, and allow a width expansion to your site by the creation of new pages.
Going back to my original point, there is a risk, SERPS to one side, that you change the nature of your site entirely - from single-source authority to community. I personally think that's the bigger question. You need to think carefully whether or not you want to do that.