re: "how often links without HTML are checked compared to links in HTML"
I rarely check out unlinked adresses as well. The old MSNBC board used to automatically detect the links, but it had troubles when the link wrapped, so there was the constant dance of copying the 2nd half of the link to the clipboard then clicking the link, hitting stop before the page timed out, pasting in the second half than hitting go.
Wasn't always worth the trouble either.
Weren't you once contemplating putting some basic text editor tools into the post window? Seems like that would be of more benefit than an autosystem that only worked half the time.
Steve