You can create a lightweight account on Medium using your Google, Facebook, or Twitter account. This is actually the same model as for SE; you don't log in to a special SE account with an SE password, but you log into whatever service is providing your credential and then sign in to SE automatically. If you don't have, or don't want to use, any of those, you can also create an email-based account there.
Once you have created an account on Medium, you can comment on any post -- on the blog there are no reputation requirements or anything like that. If you control the device you're connecting from (it's not a public computer), you can tell Medium to keep you logged in and you'll probably never have to think about it again, unless you use a new device or browser. I've been signed in on my home computer since we created the blog in 2015.
If you don't want to create an account on Medium, another place you can ask questions of most1 blog authors is chat, which you have enough reputation to use. The folks in our chat room are friendly and would be happy to lend a helping hand to a new user.
For more information about contributing to the blog, including a link to Medium's help page on creating accounts, see Want to Contribute?.
1 The blog has attracted one contributor so far who, as far as I know, isn't an active user here on Worldbuilding.SE. To reach Jasper you'll need to comment on Medium, most likely.