Background:
The description under machine name for a custom token says "A unique machine-readable name for this token. It must only contain lowercase letters, numbers, and underscores." This is properly enforced, underscores work, hyphens do not.
The description under machine name for a custom token TYPE says "A unique machine-readable name for this token. It must only contain lowercase letters, numbers, and underscores." But the if you use an underscore you get an error which says "The machine-readable name must contain only lowercase letters, numbers, and hyphens." Hyphens work, underscores do not.
Proposed solution(s)
1) Preferred: make the two consistent with the rest of drupal by using the machine name element that is included in drupal core (https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Render%21...).
Alternatives 2) make the two consistent within code so that they both allow hyphens and/or both allow underscores and make the descriptions accurate.
Alternative 3) make the descriptions accurate.
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Thanks for this patch @gadaniels72, it worked for me!
I'll prepare a MR and fix this tomorrow. Thank you all!