> all of which gives me useful info and context about the writer and their education level and the amount of effort they put into the piece and the amount of editing it underwent and so on.
From a reader centrist point of view, I can understand lamenting the loss of this information channel. From the author's stance, I can imagine wanting to tighten up alternate channels of information and present a clearer message. The author always has this ability, through natural circumstance, effort or research, so this tool would do nothing but make it easier. As a reader, it may change the assessment to whether they ran a proselint-like tool or not, but in the end those are just assumptions. The writer could be making specific choices to disregard the linting tool on purpose. In the end, reading is still an interpretive experience, this just allows authors more options.
> The way to improve genuinely bad writing is not with rules and tools -- it's with lots of reading, a little mentorship, and lots and lots and lots of practice.
Generally good advice for any thing, but I think it's worth noting that different people learn in different ways, and providing more methods for learning is generally an improvement, and opens the field to more people. Tools that look to circumvent historical methods for achieving skill often face an uphill battle from those that used those historical methods. It's easy to see why, as it looks like it has devalued much of the hard work they put into their skills. This may be true to an extent, but the gains often far outweigh this, as making a skill accessible to more people has wide ranging benefits for society in general.
In more concrete terms, I see no reason why a tool like this can't be a multiplier for mentorship and practice. At the very least it enables exposure to ideas that might not have been encountered before.