To find more blogs we need to expand our search terms to more terms blogs commonly use, and change our combination of terms. We have already started with:
comments -"0 comments" -"no comments" -"comments (0)" -intitle:comments
This is a good start, but lets add some more terms based on things that are normally found on blogs.

How blogs ask for comments? (and that is what you want)
comments - This is the obvious term to search for.
responses - Another way blogs identify comments. In fact some blogs say both comments and responses.
"responses to" - Some blogs get more specific with this phrase.
"share your thoughts" - From the friendly blogger.
"add new comment"
reply
"leave a comment"
"leave a response"
You probably don't want to use lots of these together. It is ok to use comments with the rest, but combining too many will give a lot less results.
What do blogs usually have on their comment forms?
Name - They always ask for your name. Often with many blogs this will be the text that goes over the link you leave. Be careful putting keywords, as they will be seen as spam.
Website or URL or URI or homepage- You want a site that allows a link. This is how they will ask for it.
Submit - Naturally most forms have a submit button, but what is on that button is not always common, and sometimes it is just a picture.
Subject or title - Not all sites have a subject or title for comments, but some do to narrow down.
Preview - A preview button is usually a great sign of a page that will allow html.
Post - This one often goes by each comment, but it also can go by the blog post, so it may not help much.
How do blogs check for good comments?

CAPTCHA - Those funny looking letters or phrases to make sure you don't spam.
human - Some blogs will ask human? and just have a checkbox or a captcha with this check.
"are you human" - And some will ask this way.
spam - Lots of blogs will even point out that they are filtering spam. And don't spam them!!!
Some blogs will allow html - These are the ones to add links directly.
These blogs will allow html tags directly in your post, so these can be good words to search for.
tags - Usually blogs will tell you what html tags you can use.
html or XHTML - The notification that some html can be used.
href - This is what you are after, but they are not that common.
a em strong cite code ul ol li dl dt dd - You can also try these other tags, but a won't work that often. cite is my favorite. These tags are great ones to add to your search.
http - Often a previous poster will leave a normal web address that is converted to html.
How do blogs show that they have comments?
You want to make sure a blog has at least one comment before you add yours, or you won't be sure it doesn't have the nofollow tag. You can always add the first comment, but there are no guarantees there.
"by * on" - You will find lots of blogs that say something like "comment by jeff on Sept 25, 2008" beside each comment.. Some commenters will have 2 words in their name, so you may also try "by * * on".
"so far" - Lots of blogs let you know they have comments by saying how many people have commented so far.
ago - This can be a good one. Lots of blogs will say how long ago each comment is posted.
"comment by"
"submitted by"
submitted
verified or not verified - Some blogging platforms verify their users, but allow anonymous posts. They may have these tags for registered and unregistered users. (not verified can be a good indication that you won't have to create a user account to post a comment.
-"no comments" -"0 comments" -"comments (0)" -"no responses" -"0 responses" - These are common ways blogs show they have no comments so far.
-"read more" If a result page has read more on it then you can't comment on it directly, and you won't know if the comment page has nofollow tags.
What are some other things on blogs?
RSS or Atom or feed - Blogs often want to be syndicated.
pingback or trackback or linkback - These blogs can be good for getting links back to your blog or website when you post their blog on your site.
Other stuff to weed out
-intitle:comments - You will want to weed out sites about comments.
You also may have to weed out sites about other words you use in your search query.
Other tips
This tip doesn't use the followtopia do follow search engine, but I thought it was so good that I had to include it. It is how to find U comment I follow blogs using google image search. This is a badge that people use to show they are part of the do follow movement.
Sum it up
The best way to find the best search string for your keywords is to look at blogs and try to find common words on the blogs. You will find that as you search and go through the results you can refine your search tactic. In general you will want to look a comment forms, and try to find which sets of words are together for your types of sites.
Good luck hunting for sites without nofollow. Be sure not to spam sites. Only place comments if your content is relevant. There is no better way to waste your time than to spam.
What works for you?
Leave comments to let me know what worked for you. If it is a good enough tip, I'll link to your site. Heck, if it is great tip. Write about it on your site, and I'll link to the post.

beside them in the results, and websites without the nofollow tag will have
beside them. This way you can quickly weed out websites that use the no follow tag.