I haven't personally tried this yet, but I was thinking about whether it's a good idea or not.

On the one hand, just a regular blog link will introduce the site's owner to their site, but on the other hand, if the reader's blog post is left in the website field, which may be relevant to the current blog post being commented on, does it leave a better impression? Or would it be frowned upon in the networking scheme of things?

Thoughts?

I'm not sure what you're asking, but I think you're asking what the weighted difference is between a link, say on the side of your page, versus a link within the content of your page.
If this is your question, yes, there is a difference. A link within the content is viewed by search engines with heavier weight than just a link on the page. I'm not sure how much more, however. But the best is to have what you mentioned... link within relative content.

I'm not asking about how much "weight" the link carries with search engines, but if it is a better networking tool with other bloggers in the long run.

Say for example:
I visit a health blog and comment on a post about "What kinds of drugs are affecting teens these days", or something.

But say I also wrote a post on my own blog, which isn't exactly "health-focused" but I wrote a post about the "Top 5 deadly drugs" on it, or something similar.

So basically would it be better to leave that comment with my site's main URL, or the post's URL, as it relates better to the writer's blog post. And the readers would better network with me, as they would know I wrote an article or two on my own blog about drugs.