Extending the idea, instead of “I’d use module::A over module::B”, more useful would be “I’d use module::A over module::B, for task X. And perhaps this could be combined with the tagging idea, raised by a number of people.

For example, considering all the modules related to defining constants: All modules might be tagged “constants”. Modules like Const::Fast and Readonly might also be tagged with “immutable variables”. Modules like constant and Constant::Generate might also be tagged with “constant functions”, etc.

Instead of, or more likely in addition to, the comment field, there could be a shorter text field (max 25 chars, say) for specifying the “scope” in which you think module::A is a better choice than module::B.

As well as typing your own in, it would have a drop-down menu for selecting from previously used ones. Then essentially people are tagging two modules at a time.

This could use the keywords field from the meta spec. If the module author has provided a keyword, then this might be presented as the default tag when suggesting an alternative. MetaCPAN could also let people tag modules, without having to specify an alternative, and could support basic curation, so you could say that immutable variables was the same thing as the oxymornic constant variables.

Together these would really enable a much richer MetaCPAN search experience.