2) Should the option be able to be turned off by posters that don't want their messages to have links automatically inserted, 3) Should the option be available for users that read messages to turn the auto-linking function off?

The fact that a word e.g. "bible" has an automatic link if clicked should not require a "turn it off" option. It is, I hope, not mandatory to click on the link. If I have misunderstood and the intention is that if "bible" is in the text the page will change to "the bible" without any action then do not do it at all.

Erik

Ps Craig, if you implement this, you will probably be flooded with requests for autolinks for Farnell, Pune, Mouser, P89C51RD2, Red Cabbage and who knows what else.