In the future, maybe add a tip about not putting any BBCode formatting between [url] [/url] blocks?
https://docs.godotengine.org/en/latest/engine_details/class_reference/index.html

I will try fixing the RST generator bug.

It turns out that RST cannot parse nested inline formatting (without using some workarounds):
https://docutils.sourceforge.io/FAQ.html#is-nested-inline-markup-possible

Here would be my "fix" if RST has nested inline formatting:

# New code:
link_title = text[endq_pos + 1 : endurl_pos]
    for invalid_nested_tag in ["url"]: # Use this if RST has nested inline formatting.
        if link_title.find(invalid_nested_tag) != -1:
            print_error(
                f"{state.current_class}.xml: Invalid link title for [url]: found a nested {invalid_nested_tag} tag before [/url] in {context_name}.",
                state,
            )
            break
formatted_link_title = format_text_block(link_title, context, state)
tag_text = make_link(url_target, formatted_link_title)

Found 4 more formatting issues related to nested tags: godotengine/godot-docs#11834
Also tested that all nested tags will have the same issue, e.g. [i][b]text[/b][/i] becomes **text**.

I can think of 3 ways to deal with this issue:

1. Remove all existing nested tags and add warnings, which is possible since currently there are only 5 problematic nested tags in the entire doc.
2. Remove the inner nested tags only for RST output, which is similar to option 1, but the online doc will differ from the offline doc.
3. Use replace or this workaround, which requires a lot of effort and still has some edge cases.

My new commit implemented option 1.