MyST doesn’t like that and throws a warning. I’d like to stay warning-free without spuriously ignoring warnings.

I filed #664, but a better solution for this is (and would have been for #648) to add a “initial section depth” config option for markdown instead of allowing users to customize the title section depth while not adapting the other sections.

We can kinda hack this in with the current solution as well:

if m := re.fullmatch(r"([^\n]*\n)*(?P<hashes>#+)\s.*", title_format, re.MULTILINE):
    initial_depth = len(m["hashes"])
else:
    initial_depth = 1
sec_depth = initial_depth + 1
cat_depths = defaultdict(lambda: sec_depth + 1)
cat_depths[""] = sec_depth
depth = dict(title=initial_depth, section=sec_depth, category=cat_depths)

and the template could read for e.g. the section header:

{{ "#" * depth["section"] }} {{section}}

and for the category header:

{{ "#" * depth["category"][section] }} {{ definitions[category]['name'] }}

[…]
cat_depth = sec_depth + 1
depth = dict(title=initial_depth, section=sec_depth, category=cat_depth)

{{ "#" * depth["category" if section else "section"] }} {{ definitions[category]['name'] }}