Pretty sure it's because literally all the signal.me links are the same when you remove the part after the #.
When you perform an HTTP(S) request you never provide the part after the # in the request URL, it's only interpreted by the web browser itself. It's likely that their antispam thing does the same and ignores the hash altogether.
When you perform an HTTP(S) request you never provide the part after the # in the request URL, it's only interpreted by the web browser itself. It's likely that their antispam thing does the same and ignores the hash altogether.
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Example of link (blocked): https://signal.me/#eu/P01wpUmC4nT2BBTwMrPAw7Nxcp81055tKHGbYw...
Without the hash (blocked): https://signal.me/
There is no blocking if you add any letters in the path (e.g. “abc”): https://signal.me/abc#eu/P01wpUmC4nT2BBTwMrPAw7Nxcp81055tKHG...