Jesse,

Are you sure Guix is incorrect?

  $ df -i / /gnu/store

If you're (almost) out of inodes on either, you'll have to delete 
some files.

In which case you can thank Unix for -ENOSPC meaning ‘you're out 
of something; I won't tell you what’, but perhaps Guix could work 
around its flaws by doing our own stat() and displaying a hint. 
We already warn about low storage space.  It makes sense to do the 
same about inodes.

Kind regards,

T G-R