+>> I agree, and I'll ask them to fix it (and probably refer them to this page).
+>> One reason they still have my business is that their customer service has
+>> been notably good; I always get a response from a human on the first try,
+>> and on the first or second try from a human who understands what I'm saying
+>> and is able to fix it. With a few exceptions over the years. I've dealt with organizations not like that....
+>>
+>> But I included the note here because I'm sure if _they're_ doing it, there's
+>> probably some nonzero number of other hosting providers where it's also
+>> happening, so a person setting up OpenID and being baffled by this failure
+>> needs to know to check for it. Also, while the world of user-agent strings
+>> can't have anything but relatively luckier and unluckier choices, maybe
+>> `libwww/perl` is an especially unlucky one?
+
+>>> Yippee! _My_ provider found their offending `mod_security` rule and took it out,
+>>> so now [ikiwiki.info](/) accepts my OpenID. I'm still not sure it wouldn't be
+>>> worthwhile to change the useragent default.... -- Chap
+
+#### culprit was an Atomicorp ModSecurity rule
+
+Further followup: my provider is using [ModSecurity](https://www.modsecurity.org/)
+with a ruleset commercially supplied by [Atomicorp](https://www.atomicorp.com/products/modsecurity.html),
+which seems to be where this rule came from. They've turned the rule off for _my account_.
+I followed up on my ticket with them, suggesting they at least think about turning it off
+more systemwide (without waiting for other customers to have bizarre problems that are
+hard to troubleshoot), or opening a conversation with Atomicorp about whether such a rule
+is really a good idea. Of course, while they were very responsive about turning it off
+_for me_, it's much iffier whether they'll take my advice any farther than that.
+
+So, this may crop up for anybody with a provider that uses Atomicorp ModSecurity rules.
+
+The ruleset produces a log message saying "turn this rule off if you use libwww-perl", which
+just goes to show whoever wrote that message wasn't thinking about what breaks what. It would
+have to be "turn this rule off if any of _your_ customers might ever need to use or depend on
+an app or service _hosted anywhere else_ that _could_ have been implemented using libwww-perl,
+over which you and your customer have no knowledge or control."
+
+Sigh. -- Chap
+
+> Thanks for the pointer. It seems the open-source ruleset blacklists libwww-perl by default
+> too... this seems very misguided but whatever. I've changed our default User-Agent to
+> `ikiwiki/3.20141012` (or whatever the version is). If we get further UA-blacklisting
+> problems I'm very tempted to go for `Mozilla/5.0 (but not really)` as the
+> next try. --[[smcv]]
+