I wouldn't say never under any circumstance to do this, a pun or a joke occasionally creeps into my posts as well, though I feel this is definitely a less-is-more thing.

You sometimes find texts where you get the feeling the author almost expects a sitcom laugh track over the post, and funnies are crammed into every available crevice.

To put it in perspective, I would note that the article title specifies "how to write blog posts", plural, not merely "how to write a blog post", singular. In other words, you're promoting a body of work, or for lack a better term, a "brand". If you want your brand to be authentic, it needs to reflect your personality. Thus, I think there is leeway for humor, even sarcasm, meandering, rambling, if that's what you tend to do. If you can establish a brand, an audience, then readers will stay with your blog posts because they were written by you, in spite of your style, or perhaps due to your style. Ultimately, of course, you need something interesting and/or important to say, but you don't need to present it robotically. Unless you are a robot! The negative oneth law of robotics is that a robot must not attempt humor.