Why? Because I've finally found the solution to having my chapter, etc., heads link back to the Table of Contents, and I was able to get rid of the underlinings on the hyperlinks and to eliminate the border around the hyperlink targets.
That's worth a yelp of joy, if anything is.
If I were a really nice, helpful indie publishing blogger I'd reproduce the code from the style sheet and the HTML right here for all to see. But if I do it once . . .
Well, if anyone trips over this post and is interested, leave a note in the Comments and I'll edit the post with it in.
One thing that disappoints me, though: I joined the ebook forum at Stack Exchange last week to get the answer to this very question. Even though I included the non-working code, no one has come up with a single suggestion for how to solve it. One member posted a comment asking why I want to do bidirectional links on my TOC in the first place; doesn't the Kindle system take care of that?
And ya know? Now that they mention it, I confess I've forgotten why I've been so passionate about it. Maybe it's just that it seems dumb to have a hyperlinked table of contents that's only good when you're at the beginning of the book. If you're going to leave it all to Kindle, why include your own TOC in the first place?
Anyway, it works. I still have to see if I can get my chapters (all 78 of them) to nest under the division heads, but I think I'll leave that till tomorrow.