Very interesting! Just the other day I've tried proselint for the first time, and became annoyed that I'd have to hack something together to only have it lint over the text in my markdown file. It doesn't ignore code blocks, as it just supports text, as is not aware of any file format.
Vale seems to do this out of the box, which is great, but the suggestion I get, while better than nothing, are still very rudimentary compared to Grammarly[1] (which I haven't used for at least a year at this point).
For example, I've enabled all styles. The alex and write-good ones gave actionable suggestions. Readability however had suggestions of the form "Try to keep the Automated Readability Index (8.83) below 8.", "Try to keep the SMOG grade (11.35) below 10.", "Try to keep the Coleman–Liau Index grade (9.57) below 9". If I knew what that was maybe I could improve my score. Is there another FLOSS tool that can turn those in actionable steps?
[1] And LanguageTool, even if sometimes advertised by FLOSS folk as a Grammarly alternative, it really isn't. Every time I try it, I feel disappointed. Has anyone tried their premium option to see if it's better?