[Epistemic status: Was originally going to be a comment, but I decided to make a post because the topic seemed to be of general interest.]
I'm not sure how I feel about the idea that people should familiarize themselves with the literature on a topic before blogging about it. Here are some perspectives I've seen on each side:
My current hunch is that it's good for people to write blog posts about things even if they aren't familiar with the literature (though it might be even better if they wrote their post, then became familiar with the literature, then edited their post accordingly and published it).
In machine learning, "bagging" approaches where we combine the output of lots of classifiers which are each trained on a subset of the training data often outperform a single complex model with access to all the data. This isn't necessarily an argument for the wisdom of the crowd per se, but it seems like an argument for the wisdom of a reasonably informed crowd of people coming at something from a variety of perspectives.
When I read about highly creative people (Turing award winner types--this might be more true in computer science than other fields), a recurring theme is the importance of reinventing things from scratch without reading the thoughts other people have already had about a topic, applying ideas from apparently unrelated fields, and more generally bringing a novel perspective to bear.
Even absent the benefits of originality, I think reasoning things out for oneself can be a great way to internalize them. ("What I cannot create, I do not understand" - Richard Feynman.) The argument for publishing is less clear in this case, but you could think of a forum discussion as serving a similar purpose as a recitation or discussion section in a university course, where one gets to examine a topic through conversation. You and the people who comment on your post get some social reward in the process of thinking about a topic.
However, I'm also worried that if a blog post about a topic is more accessible than a journal paper, it might end up being read by more people and factored into our collective decision-making more than it deserves on a purely epistemic basis. Of course, people are already spending much more time reading Facebook posts than journal papers--probably including people in the EA movement--so it's not clear how to think about the harms here in general. (For example, if reading the EA Forum usually funges against Facebook for people, and EA Forum posts are generally higher quality than Facebook posts, that seems like an argument for more EA Forum posts.)
In any case, you can mitigate these risks by marking your blog post with an epistemic status before publishing. It certainly seems acceptable to me to link to a relevant paper in the comments of a blog post about a topic that has been covered in the literature (e.g. "Author X [disagrees] with you"). But I think it can be even better to additionally summarize the argument that Author X makes in a way that feels personally compelling to you and take the opportunity to re-examine the argument with fresh eyes--see my previous complaints about information cascades in the context of Effective Altruism.