Indeed, there's no evidence in canon that Azkaban has ever been used to hold a Dark Lord.
I suppose this depends on what we consider evidence. I would personally assign high credence to that based on 2 considerations:
1) that there have been quite a few Dark Lords, such that they are considered a generic natural category and are spoken of collectively; the Harry Potter wikia includes a list of 9 wizards/witches who don't appear in canon events, but I'm not sure on what basis they are listed. 2) the only other Dark Lord whose disposition we know of was put into an institution much like Azkaban, but not Azkaban for at least 2 plausible reasons (Grindelwald having built that prison himself, leading to it being poetic justice that he be confined there rather than Azkaban; and having rampaged mostly over Europe, and not Britain.)
Given that Grindelwald was not given the death penalty, it seems reasonable to think that captured Dark Lords are not executed out of hand, but imprisoned; and where to imprison the many Dark Lords but Azkaban?
Given that Grindelwald was not given the death penalty, it seems reasonable to think that captured Dark Lords are not executed out of hand, but imprisoned; and where to imprison the many Dark Lords but Azkaban?
What basis do we have to suppose that there have been many dark lords? There have certainly been multiple dark lords, but canon provides us with a grand total of two examples, and the gap between Grindelwald and Voldemort was implied to be atypically short. We don't know how far back the history of Azkaban goes, and how many Dark Lords have been contemporaneous with it. We only know that the one canonical example of a dark lord who was imprisoned, was not imprisoned there.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.