I think blogs should have a universal comment function, I'd love to engage ith the author but many blogs don't bother providing a basic textarea.
They typically do but are disabled due to the volume of spam and moderation overhead. Send an email.
I think policing all the spam isn't worth the trouble.
Send the author an e-mail.
The universal contact function is usually there, and it's email. I tried many times: it works. Authors respond. Only very few people seem to want to keep it hidden.
I'm dumbfounded by the number of times I see comments of the form "if the author is reading this ..." on a 3rd party comment side, with a link posted by somebody else, on a forum the author is likely never going to watch, followed by an actually useful comment that you could have _ensured_ the author reads by you know... just contacting him?
Forum comments are just recipe for instant spam, and have been so in the last 10+ years. If you want to make them useful, it currently needs to be actively policed (not to mention: you can be responsible for the content posted as well in several countries now). As an author, only if you're trying to create an audience around your blog, all the hassle around it might be worth it.