Yes, that would be nice, although I'm not sure how implementation would work. You need something to anchor the toots to the post. The logical choice is the URL of the post. However, this can be accomplished already with webmention and doesn't need ActivityPub at all. You have to use something like Bridgy to monitor your account for your domain and then pass them to webmention. Unfortunately, Bridgy can be a little finicky.

I used to use a WordPress plugin that allowed people to post comments using their social media accounts, but that was just for verification and it wasn't an integration with social media.

My understanding is that followers will only see content from the time they subscribe/follow forward. As Zak mentioned in another comment it's not that they can't, but the platforms choose not to. That said, I don't use the website as my daily fediverse account for a number of reasons. The integrations I use allow for comments, likes, and boosts to be captured, even if they're not replying to a post from my blog account.

Also, if someone looks up my blog on Mastodon they get a message saying previous posts can be found on the original site with a link to my author page.

I agree, that the implementation has its issues, but it's a start. Version 2.0 is supposed to drop in a week or two, which brings some needed enhancements. I didn't realize that the lack of post history was Mastodon-specific. However, when I try to view my blog through different sources I have the same issue, so maybe that's a standard practice?

For some reason it posted the image and not the link. I've updated the post, but here's the link as well. https://jseggers.com/technology/how-to-set-up-activitypub-for-self-hosted-wordpress-sites/

My experience has been that the "Hot" view is most similar to Reddit if you're looking for new content. You can read about the different sorting here: https://join-lemmy.org/docs/en/users/03-votes-and-ranking.html

What I've noticed about the "Active" sort is that older posts that are still getting upvotes and have new comments can remain at/near the top of the list for several days. I think this is good if you want to see where ongoing discussions are happening. On Reddit, I often felt that an interesting post fell off my view very quickly. I know I wasn't the only one, which is probably why people would post a "remind me" post or "following" post on Reddit so they could come back to it later. Regardless, someone might entirely miss a post that blows up in a community but sees it in the "Active" view and check it out. I like "Hot" because I can see what's trending up, but I frequently switch between Hot and Active. I've noticed that many of the "hot" posts don't have any comments.

I agree with you regarding quieter communities. Reddit had something in its sauce that allowed posts from less active communities to show up in my feed through all the noise of busier communities. This didn't happen for all the subreddits that I joined, but rather, the ones I showed an interest in. The downside of that kind of algorithm is it reinforces the echo chamber effect as the algorithm is learning what I like and then showing me more of what I like to get me to stick around longer. This system isn't (currently) prone to that kind of manipulation.