I am strongly in favor of our very best content going on arXiv. Both communities should engage more with each other.
As follows are suggestions for posting to arXiv. As a rule of thumb, if the content of a blogpost didn't take >300 hours of labor to create, then it probably should not go on arXiv. Maintaining a basic quality bar prevents arXiv from being overriden by people who like writing up many of their inchoate thoughts; publication standards are different for LW/AF than for arXiv. Even if a researcher spent many hours on the project, arXiv moderato... (read more)
Here's a continual stream of related arXiv papers available through reddit and twitter.
I should say formatting is likely a large contributing factor for this outcome. Tom Dietterich, an arXiv moderator, apparently had a positive impression of the content of your grokking analysis. However, research on arXiv will be more likely to go live if it conforms to standard (ICLR, NeurIPS, ICML) formatting and isn't a blogpost automatically exported into a TeX file.
I agree that formatting is the most likely issue.
The content of Neel's grokking work is clearly suitable for arXiv (just very solid ML work).
And the style of presentation of the blog post is already fairly similar to a standard paper (e.g. is has an Introduction section, lists contributions in bullet points, ...).
So yeah, I agree that formatting/layout probably will do the trick (including stuff like academic citation style).