They would enable us to:

• keep doctest annotations sufficiently fine-grained for the purposes of test coverage in modularized tests
• reduce the visual clutter in source code and formatted documentation
• reduce the maintenance effort (in particular when using primitive text editors).

See

• https://groups.google.com/g/sage-devel/c/utA0N1it0Eo/m/RMUBMbtbAgAJ and references within (sage-devel, 2023-06)
• Discussion on naming of the keyword for standard features: https://groups.google.com/g/sage-devel/c/OUnoroIf0qc (sage-devel, 2023-06)

Switching from the current line-level annotations to block-level annotations (where it makes sense) can be easily automated. We should include such an automation tool in Sage. It would complement the other development tools provided to assist with modularization tasks. That's:

• Doctest # optional / # long / # needs annotation maintenance tool #35790

See also:

• PDF documentation: Replace # optional by footnote symbols #35726

Part of:

• Meta-ticket: Modularize sagelib into separate distributions (pip-installable packages) sagemath-... for Sage 10.x #29705