Context: LaTeX is a typesetting system. When compiling a document, a lot of really in-depth debugging information is printed, which can be borderline incomprehensible to anyone but LaTeX experts. It can also be a visual hindrance when looking for important information like errors.
Wise words, and true most of the time.
But goddammit is it so hard not to write over the page border? This isn’t something I should have to specifically define as bad.
You don't generally have to. There's a package or environment somewhere that lifted that restriction or force it by trying to do something else. LaTeX is 100% deterministic. Someone, you perhaps unknowingly, told it to put that text there while trying to achieve something else.
Remember that LaTeX is about setting rules then letting it arrange the text in a way that follows those rules. If you try to meddle into the typography by hand, forcing specifics that break the rules, you will break its behavior. If it is putting text over the margin, it is because it determined that is the only way to fulfill the totality of your instructions.