LiveJournal users can now authenticate (to post comments on my older entries without a delay) by entering their LJ usernames in the comment form.
(So far I've only set this up on the individual-entry pages. Once I'm sure it works, I'll add it to the popup window comments-only pages as well.)
Thanks much to Mark Pasc(?)'s excellent OpenID Comments for Movable Type plugin, version 1.6.1, which not only allows OpenID authentication but also has a special case for LJ.
If any of you are using OpenID but are not using LJ, lemme know; I could also provide a general OpenID signin form. But I suspect that at least 99% of the people who are likely to comment here and who use OpenID at all are using LJ.
Note to LJ users who have no idea what I'm talking about: LJ automatically provides you with an OpenID page. So all you have to do is enter your LJ username in the text box when you want to enter a comment on one of my older entries; you don't need to know anything at all about OpenID.