Slugs get a bit weird readability-wise because the system doesn’t strip out the HTML or Markdown first. Slugs should be generated from the plaintext.
ETA: For example a URL like
is… kind of no.
ETA: FWIW, I might not even care anymore about customizing slugs if the slug creation process stripped the HTML/Markdown first. (Although my OCD would probably then also want it to ignore all punctuation including periods, so URLs are always a consistent length instead of sometimes being four words because a post starts with a four-word sentence.)