how to reply to a post
One way is to write your own blog post that links to it. It's pretty nice — you own your post, they own theirs, both of you get to format and organize them the way you want. If you want the other person to read the reply you can send it to them out of band, and if they like your reply they can reply further and/or edit their post to link to yours, but neither party is obligated.
Some things about this are a little weird though, mainly when the reply disagrees with the original post (and, unfortunately, more replies are born of disagreement than agreement). If you're a lot more popular than them, you can ruin their day with unwanted negative attention; they have little recourse but to delete their post1, which can then render your reply nonsensical if it refers to their post extensively. Also, by linking to the post, you're promoting it in a way, which you might not want to do if you disagree really strongly. Even worse, on some platforms the algorithms are wont to interpret your actions as a suggestion to show the original to more people.2 I associate these dynamics with Twitter quote-tweets a lot, though honestly this is all secondhand. I'm hopeful that things aren't so bad among blogs when there's more room for nuance and fewer engagement-focused algorithms, but I don't think that completely eliminates the pitfalls.
Another way to reply, then, is to not refer to the original post at all. Say "I read somebody arguing that X, but I actually think not-X." Then, delete the first part and simply say that you think not-X. For all the above reasons, this is usually what I opt for when disagreeing, but it does feel a little... cowardly, perhaps, like you're talking about somebody behind their back.3
And, sometimes disagreeing is constructive and they do want to know about your post anyway. If I'm wrong about something, I would like to be convinced to change my mind! Even if not, I might like to know that somebody has read and absorbed my writing to the extent that they took the time to write a counterargument.
I think the ideal scenario works out to if you already kinda know them, perhaps from chatting about prior posts you do agree with — you've developed a guanxi to fall back on — and can just DM comfortably. This obviously isn't practical to achieve every single time, plus it's tougher if you're posting on a platform that doesn't support DMs. But perhaps it's a helpful goal to strive for.
which, to be clear, I consider to be their prerogative. Screenshotting or externally archiving with their name still attached has always felt to me like snitching behavior unless they're much more popular than you.↩
and sometimes this is "the point", but going into this would take me too far afield. cf. The Toxoplasma of Rage↩
Another downside I can list, though not one I'm overly concerned with: it runs the risk of my readers thinking, surely X is a strawman and nobody actually thinks so, why are you wasting your breath arguing against it?↩