r/AskHistorians has relatively high standards regarding what they look for in an answer, specifically in-depth knowledge of the subject that goes beyond the first page of hits on google or Wikipedia articles; and a fairly large and dedicated mod team. The mods routinely police the threads and remove questions and answers that don't meet the submission guidelines. Of course, when one of the threads gets very popular very fast, it can hit r/all - which attracts a lot more visitors - and you can get a deluge of low-quality posts from folks more familiar with r/AskReddit. In which case it can become a comment graveyard, with hundreds of replies removed. But most of the time, any bad or poorly sourced or joke comments are removed, so that the good answers can flourish.

You might not always get an answer to your question on r/AskHistorians, but you're not likely to get a bad or incorrect answer!

Every comment isn't deleted. But this subreddit is different from other subreddits, as it is primarily focused on high-quality answers to questions, not discussion. It can often take time for a good answer to be written. The mission of /r/AskHistorians is to provide users with in-depth and comprehensive responses, and our rules are intended to facilitate that purpose. We remove comments which don't follow them for reasons including unfounded speculation, shallowness, and of course, inaccuracy.

Of course, we know that it can be frustrating to come in here from your frontpage or /r/all and see only [removed], but great content is produced on this subreddit every day, and we hope that you will check out places they are featured, including Twitter, the Sunday Digest, the Monthly "Best Of" feature, and now, Facebook.

Further to this - comments are sometimes deleted but the author isn't even made aware that the comment has been deleted, let alone why.

Would it be possible to let people know when their comments have been deleted even with just an automated response along the lines of "Your comment has been deleted, please consult the rules in the future"?

In case you are wondering why there are no [answered] flairs added to questions, you should take a look at this Rules Roundtable where this topic is discussed in depth.

I usually ask something here for the papers I am writing for homeworks or so, therefore I need sources to put in the reference list. Sure, it takes a lot of time to get a proper answer, and sometimes my question is not answered at all but I need proper sources -books or articles, not guesses or Wikipedia links. That's why I ask my question here, and it helps.