There seems to be some confusion on commenting on a blog, editing comments, and contributing.
If you want to comment on someone’s blog entry, please do so there rather than writing an email to that person. An email is fine, if you want to take the conversation “off line”, but it’s best to comment under the post so all can see the comments made and how they build, argue, take the conversation in different directions. Sometimes there is as much value to gain from the comments as they are from the posts.
Unfortunately, I do not know of any blogging software that allows you to post a comment then, once it’s posted, to go back and edit if you want to change the comment. You can, however, post an update to your comment. If there are several comments in between your new one and the original, copy and paste the passage in question into the new post as a way to direct a reader’s attention to the point in question. Misspellings and grammar error, as long as they are not horrendous, can be left alone, but that’s a personal preference.
As far as contributing, several of you are correct: In most instances, blog software (either free, hosted, or self-hosted) require you to register, not only to make comments, but to contribute as well. For me to invite you as a contributor to this blog, I need to send an invite to your WordPress account, not to your email, blogger account, or MySpace
I’ve purposely held off doing this as I wanted you to have a few weeks to get used to the process. Now that you have some experience moving around blogs, I will probably invite you to contribute to this blog. This invitation will be a separate post, however.
The chief reason registration and invitations are done is spam. The logic goes that if someone is going to take the time to register, he or she must be serious and not a spammer. Also, this protects against automatic bots finding blog sites that allow anonymous posts so it can spam them. In most cases, or at least the softwares I’ve used, turning on and off comments are a user option. If you’re comments are off, check the dashboard and preferences for a way to turn them on.