DISCLAIMER: It is entirely possible that Kleopatra's notepad is supposed to support encrypting rich text, in which case this bug report is invalid. However, I believe decryption/verification of rich text should not fail if the content is valid PGP.
Relevant KDE bug report here: https://bugs.kde.org/show_bug.cgi?id=421216
When posting from a rich text source (e.g. a browser or LibreOffice), Kleopatra's notepad widget will accept the formatting. For encrypted messages from such sources, verifying or decrypting may fail.
Attached document (KDE bugtracker): https://bugs.kde.org/attachment.cgi?id=128273
STEPS TO REPRODUCE
- Download attached test file. It includes a PGP signed message with some formatting. I used this key to sign the message: https://keybase.io/iswz/pgp_keys.asc?fingerprint=618c5b0e104a3043b2fd520ad80a4cf9997f2abf
- Copy and paste contents into Kleopatra's notepad and click "Decrypt / Verify Notepad".
OBSERVED RESULT
With certificate:
Ian Schwarz <ian@datacube.xyz> (D80A 4CF9 997F 2ABF)
The signature is invalid: Bad signature
EXPECTED RESULT
Signature created on Samstag, 9. Mai 2020 11:21:33 CEST
With certificate:
Ian Schwarz <ian@datacube.xyz> (D80A 4CF9 997F 2ABF)
The signature is valid.
Removing the formatting by pasting into Kate before pasting it into Kleopatra's notepad leads to the verification succeeding.
I have created a pull request on GitHub (https://github.com/KDE/kleopatra/pull/1).