That’s still known issue, linkify doesn't accept urls with underscores · Issue #38 · markdown-it/markdown-it · GitHub, workarounded with <link> (angle brackets around link). Nothing new to report.
Still no deadlines. Good news is: i finally rolled out to production my new forum software https://rcopen.com/ (why a lot of resources been spent to create markdown-it). So, chances to fix this bug changed from “far infinity” to “some future” 