I think anyone ever trying to write a paper or book with images in it using tools like LaTeX knows how bad it is to let the tool position images for you. It's always wrong, and one of the first things you learn is how to pin the image in between the text lines/paragraphs you wanted it to be between.
Text-to-diagram tools like PlantUML (and arguably even Graphviz) make this mistake too. The moment you put more than a couple things in your diagram, you discover that auto-layout can't ever make the result readable, and you look for ways to pin parts of the diagram relative to other parts; something these tools don't let you do either.
And then all three classes of tools here - HTML, typesetting, diagramming - violate the principle of least surprise in the nastiest of way: make one little change, add a letter or word somewhere, suddenly the result looks nothing like it was before, as the auto-layouting flips everything around.