If you can verify ¹ that a message has a valid ² signature from this ³ certificate:

1 - You can be sure that it was written by me, and not an impostor;

2 - It is very hard for me to deny having written it.

Certificate details:

User-ID: Judicious Use of Deadly Force (http://gtm.steamproxy.vip/profiles/76561197987815569) <judicious@gmx.us>

Fingerprint: 566CD0EDFF54E339BDDFE363BFA61C8991A38E8C

Public key:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: GnuPG v2
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♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥♥+soSqYVIuMGbLQwTEFvc
ypuzb7y/Tm6Ru7/jIZgG3b6S2NeLUun4mYF+QqgvThQ1vmLfChTDdBWhUSCFrsy4
ChNBgBrIXyVlpBxmDad6JrHtXuZZlHl1iouzxrNIJ8h+O0Mh7im8w5qux6sCBqqX
4SYwoTLPOwT+Ktdzk02rvBv68bpLDZroRtaPbL0kOaXW16jw1SBCMMvKuP4zPyJO
gqiFXnsJb8W8khi26We2gAPhVTFJ7mSOWe6ZKSpwi8/Q3ZPe8GjhDMbdqGq94UMZ
Dpo9iKEkqQuRF9d1DjuzZIxQ/I519TsG5YGUhr/y37wMk/lufLNoSjw/crPixC3O
2zkkoTLfEIBNuUrbeYiK4fBq07P+/m4T/S2yB0g/qkKmle8hSeJgeWohoQCH0D4z
Vam4jCp1ZF7wpOJcF43H7bLE8RmZhpUZQ0K2EE6CR9NN65zRtGSX5wQbcmfwbBwV
ZFMTZ8w=
=TJkR
-----END PGP PUBLIC KEY BLOCK-----

Notes:

¹,²: You need to use software to verify PGP signatures. If you're new to it, read:
https://ssd.eff.org/en/module/introduction-public-key-cryptography-and-pgp
https://en.wikipedia.org/wiki/Public-key_cryptography
https://en.wikipedia.org/wiki/Pretty_Good_Privacy

Then, if on Windows, go to:
https://www.gpg4win.org/

Read the Gpg4win manual (documentation) and then use it to verify signed messages and sign your own messages.

³: It is important, when verifying signatures, to make sure you are in possession of the actual public key you expect to be handling: One common attack consists in deceiving the recipient of the signed message to download a spurious public key, and then sending him messages signed with it. Evidently, if you think you're using Alice's public key to verify her signed messages, but instead you're using Mallory's key, Mallory can now impersonate Alice by sending you messages signed with his key. Therefore, to avoid this possibility, you must make sure the certificate you have for Alice in your key manager really is Alice's certificate. This usually entails downloading it from a secure and authenticated channel (you're sure whom you're talking to, and you're sure the message is not corrupted in transit), or using a secure channel to check the key integrity by comparing fingerprints. In the case of my public key, above, for example, make sure you're accessing my Steam profile page with 'https' on your browser. Alternatively, get my key fingerprint on my Twitter account (the fingerprint is in the bio, and in one of the first posts): https://twitter.com/Judicious_UoDF , and check it against the fingerprint computed by your own manager after importing my certificate, above. (Make sure you're using 'https' to access Twitter, as well.)

See also:
https://en.wikipedia.org/wiki/Man-in-the-middle_attack