But this could be a "legitimate f-up". Normally, most of these unsafe-url protection and detection is automated in something with the scale of Twitter.
Just like URL-shorteners often are (were?) "seemingly randomly" banned, because a portion of the shared urls are pointing at malware/phishing/otherwise banned content, all urls from this shortener get banned. It may be that signal.me is simply picking up on amount of illegitimate links. Signal is clearly growing strong. Therefore signal.me links' are increasingly seen by Twitter. Most legitimate links, but the amount of illegitimate links will then also increase.
This would trigger an automated ban¹.
The real problem then is that even if it was deliberate (conspiracy theory: Mark messaged Elon: Pls help me curb the growth of the biggest competitor of Whatsapp?) twitter can easily hide behind "overzealous automation, sorry".
¹ Especially if this automation isn't maintained properly, finetuned and kept being tweaked by teams of experts - many of which left or were layd off after the aquisition of Twitter.
2. Why it isn’t getting banned on other social networks and only on X?
3. Didn’t X previously block Substack and Mastodon URLs?
https://jatan.space/moon-monday-issue-175/