Hi there.

What you're seeing is not actually a bug or anything of the sort, but is indeed a feature of our moderation. We have higher standards than many other subreddits when it comes to providing answers for the questions posted to /r/AskHistorians. As such, we end up removing a lot of subpar, incorrect, and low effort content that fails to meet these standards.

Unfortunately, Reddit (the website) does not update the comment count that appears for threads, even when items are removed by us or deleted by the authors of comments (which we have most certainly protested and the admins have clearly neglected to address). This means that when a thread gets really popular, we end up removing a lot of rule-breaking comments that, despite being removed, remain as part of the overall count. To help mitigate this, try the browser extension developed by a user that helps to provide a more accurate comment count.

Furthermore, if content is what you're looking for, there is actually plenty of content that passes muster, but that many fail to see for a variety of reasons (for example: they only visit popular threads, they don't give enough time for an answer to be provided, they only look at threads they're interested in, etc.). To help with this, we compile the week's material into a post called the Sunday Digest! We also repost much of our content on our Twitter and Facebook. We implore you to check out those features to get the content you're looking for.

The first link in the Automod autopost should answer your question nicely; for further information, this Rules Roundtable of late June on the topic is also a good read on the matter.