My pet peeve about developer blogs is people who have only been using a language (or framework, or whatever) for a couple of weeks writing about their experiences with it. Sorry, but I'll find your experiences interesting once you've shipped a significant chunk of code in that language, let's say after half a year of full-time experience. If I want to know what it's like to write a toy application in that language, I'll just do it myself, not read a blog post about it written by someone with only a superficial knowledge of it.
> Blogging about blogging
That's something we can agree on. If a "developer blog" has an article called "Why Every Developer Must Have a Blog", it's a strong signal of low quality content - it tells me that the author apparently likes to make sweeping generalizations without thinking about what they're saying. Either that, or they have nothing interesting to say about more substantive topics.
In fact, I suspect that blog posts like "Here's What I Have To Say About Rust After Using It For Two Weeks" are usually written by people who have just read an article about "Why Every Developer Must Have a Blog" and are now convinced that they desperately need their own blog, despite having nothing interesting to say.
> No code syntax highlighting
People have different tastes. Personally, I find it very distracting to be looking at code in a rainbow of different colors, with tokens like identifiers, keywords, numbers and strings all screaming for attention due to their unique coloring. All these types of tokens can be easily identified without syntax coloring if you're familiar with the syntax of just about any programming language. (The only syntax highlighting I ever use is to make comments slightly less emphasized than code.)
> Having an always visible side bar with your profile picture staring at the reader
Another thing we can agree on. What someone looks like has no bearing on how interesting their writing is, and I find it creepy to have someone staring at me from the screen while I'm trying to read.