In your example abseil-faster-strsplit-delimiter.rst , The double blank line in the html doesn't give much delineation between the before and after code and the next example.
There probably isn't a convention per say (which is a shame), across the docs we do a mixture of different styles
But there is a desire by some of the regular clang-tidy reviewers to make the documentation consistent
It may not be ideal but the "Before/After" style, that is used in modernize-use-emplace, modernize-use-using,readability-braces-around-statements,readability-identifier-naming and readability-redundant-function-ptr-dereference does help a little.
I'm not saying looks better, but I've added a couple of examples of formatting the strsplit example for comparison, feel free to ignore.
I like those examples!
Would it be reasonable to update all of the abseil-duration-* documentation in a separate pass, after this change is submitted?
The code looks good, but I have a concern about the check name -- double seems a confusing word, see my comment.
nit: s => S; might be inline the Scales?
The double word may cause confusion easily -- at the first glance, I thought that it means convert the absl::Duration to the double type, but it turned out not.. How about using abseil-duration-necessary-conversion?