List of steps to reproduce (step by step, including full links if applicable):

• Get blocked (login user), or access anonymously from a blocked IP address (NB: this block need to be placed locally)
• Visit Special:CreateAccount

What happens?:

Wikitexts in system message "blockedtext" stay plain.

What should have happened instead?:
They should be parsed. Noticed Special:CreateAccount disabled JavaScript for security reason, not sure if this is relevant.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.:
1.39.0-wmf.9 (6393713)