From The Collaborative International Dictionary of English v.0.48 [gcide]:
Mackle \Mac"kle, v. t. & i.
To blur, or be blurred, in printing, as if there were a double impression. [1913 Webster]
I wrote these macros back in 2017, when learning my way around (t|g)roff and digging around the internals of the already existing macro packages, and they are not intended for actual use. They are, as it stands, broken for anything more complex than an article with a few pages and no notes, and both the venerable -ms and the more modern -mom would be a better fit for that use case.
This code is only published in the hopes that it might be useful for someone looking to use troff or write their own macro package, as anachronistic as that might be. It is licensed under the terms of the MIT license (see LICENSE).