Comment including special characters causes Internal Server Error #5

Descriprion
When submitting a comment to a post and if the comment includes special characters, then I get an error: Internal Server Error
The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

this happens if i comment for example

• pöö
• jee!
• oho?
• e@mail
• ..

it does not happen if I comment

• 1
• a

Steps to reproduce

1. Start the app using docker compose up
2. Log in with valid username and password
3. Click on a post title on the frontpage
4. Write a comment that includes a special character
5. Click Submit

Expected behaviour: Post comment succesfully

Actual Behaviour: Return Internal Server Error

Environment Details
OS version: Ubuntu 24.04.2 LTS
App version or git commit hash:
Docker version: Docker version 28.3.3, build 980b856
Python version: Python 3.12.3