UPDATE: Stacy emailed to say that she never could get the fix I found on Bad Example to work -- a link to the old comments appeared, but they showed up at the beginning of the entry, and she couldn't get them to show up in the normal spot at the end of each entry -- and she went with another suggestion that after much trial and error did work. The solution that worked for her was found in this entry on HaloScan's support forum, and Stacy writes that she "had to place the first code in twice at different places in the HaloScan codes." As always, your mileage may vary, but it is possible to display both kinds of comments.
Today I found an answer for a blogger with a technical problem [or so I thought -- see above], and it's a common enough situation that I thought it would be worth writing up for general perusal.
BatesLine has always been, and probably always will be, a Movable Type blog, but many bloggers, maybe most bloggers, use Blogger to power a blog at blogspot.com or for a self-hosted blog.
Starting a blogspot blog has the advantage of not costing any money, but it does have its limitations. At one time, Blogger had no comment capability, so most Blogger users used a comment service by HaloScan. Blogger then began offering comments, better in some ways than HaloScan, more limited in others. HaloScan also offers trackback, which isn't yet built in to Blogger. So it's a fairly common thing for a blogger to enable Blogger comments, get frustrated with certain limitations, and decide to switch to HaloScan.
The problem is that in making the switch, all the comments created in Blogger seem to vanish. Some theoblogical [sic] speculation posits that the Blogger comments have gone on to their eternal reward. In fact, it's more like "Honey, I Shrunk the Comments." They're still in the database at blogger.com, but after converting a blog to HaloScan comments, all links to the comments have disappeared, and they can't be seen.
There is a way to fetch the old comments back from the Great Beyond, and I'm happy to report that Ouija boards and un-shrink-rays are not involved. When I saw the plea for help on the HaloScan-beset blog (an entry on Not a Desperate Housewife), I remembered having seen both types of comments displayed on some other blogs, and a bit of googling came up with the QUICK AND PAINLESS GUIDE TO ADDING HALOSCAN COMMENTS WHILE KEEPING YOUR OLD BLOGGER COMMENTS VISIBLE on Bad Example, a blog which offers many other helpful blogging tips. I posted a comment with that link, and after a certain amount of template tweaking, non-desperate-housewife Stacy has everything working beautifully. [UPDATE: See note at top -- the Bad Example solution did not work for her.] If you visit her blog, you'll see links to the old Blogger comments and the new HaloScan comments side-by-side. (See above to see what was actually involved in getting it to work.) She should be able to go into Blogger settings and set the default Blogger comment policy to "New Posts Do Not Have Comments," so that new posts will only show links to HaloScan comments and trackbacks, while Blogger comments on old posts will remain accessible. Unfortunately, there doesn't appear to be an easy way to close off all old posts to new Blogger comments -- you have to do it one entry at a time.
The Bad Example tip sheet carries an important warning which applies to all bloggers, regardless of which content management system you use: Always back up your template before making changes. In fact, you'd be wise to back up your template even if you aren't making changes. (Blogger has been known to make templates disappear without warning.)