Comment by heavyset_go

No, if you're doing something sensitive that can get you or other people arrested, locked up, hurt or killed, you should not be using Signal for that. You should reconsider using a phone or computer at all. If you must, you must be desperate and I pity the situation you must be in, and I hope you really understand what your risk profile is, what technology can address actually it, and if that technology actually exists.

States can use metadata from Signal and ISPs to confirm that party A was in contact with party B and at what times, for example, in charges of criminal conspiracy. If one device on any end of the chats is compromised or confiscated, chats and identities are exposed. Once both devices are confiscated, messages are decrypted on both ends of the Signal app and authorities can grab the message content they used the metadata to get a warrant/subpoena/order for.

Similarly, Signal can be gag ordered to keep a record of phone numbers linked to identities if it already doesn't exist in their implementation. Signal and/or Google/Apple/ISPs/carriers can be compelled to follow wiretap laws and collect more data on specific users, push special updates to them, etc.

It's an app that forces the use of cell phone numbers linked to real identities in order to use it, clients have servers hardcoded, clients make direct connections to servers, etc. Just the first fact alone should be a red flag if your well-being depends on privacy.