People should not be downvoting you. You are absolutely write: numbered heading level is a non-modular abomination.
edit: Oh I see, yes the title shouldn't just attribute, but there is no deep reason for that, just HTML convention. I would rather what you wrote than the status quo.
Au contraire, displaying is a concern for CSS, not for HTML which is supposed to show content. In the only sense that bold or italics are appropriate in HTML is in that they sometimes transmit a meaning that can be reduced to "italic" or "bold", it would be more expressive to transmit however that <!>something is important<!/> or that it has <foreign>gravitas</foreign>.
Similarly the title of a section can be displayed with bold, or not at all, or as part of the index in the front page, or at the index at the end, or in a hovering table of contents that displays while you scroll the page, and it may be bold, big, or blue or small. All of that is a matter for the styling document, not for the content document.
The content only cares that this part is the Reptile part, not whether the R in reptile will look like a dinosaur, that's a job for style="ornamented-initial:dinosaur where the loop of the R is a mouth, and the two lower lines are the feet and the tiny t rex arms.", which would probably only be interpretable by a browser connected with a stable diffussion model.
edit: Oh I see, yes the title shouldn't just attribute, but there is no deep reason for that, just HTML convention. I would rather what you wrote than the status quo.