proselint is a turbocharget spellchecker

proselint, a linter for English prose. A linter is a computer program
that, akin to a spell checker, scans through a file and detects issues
— like how a real lint roller helps you get unwanted lint off of your
shirt.

proselint places the world's greatest writers and editors by your
side, where they whisper suggestions on how to improve your prose.
You’ll be guided by advice inspired by Bryan Garner, David Foster
Wallace, Chuck Palahniuk, Steve Pinker, Mary Norris, Mark Twain,
Elmore Leonard, George Orwell, Matthew Butterick, William Strunk,
Elwyn White, Philip Corbett, Ernest Gowers, and the editorial staff of
the world’s finest literary magazines and newspapers, among others.
Our goal is to aggregate knowledge about best practices in writing and
to make that knowledge immediately accessible to all authors in the
form of a linter for prose; all in a neat command-line utility that
you can integrate into other tools, scripts, and workflows.

Slackware users can access proselint in Emacs with minimal
configuration, using flymake. (Or install flycheck from MELPA.)

proselint should be extensible. If Slackware users find out that some
plugins are advisable, feel free to contact the author to package some
them.