When viewing an issue through a board or its full view, with the "New Jira issue view" and dialog mode both enabled, the size of the comment box cannot be changed.
Add the ability for users to resize the comment box.
This should enhance greatly the user experience.
As a workaround you can use ctrl+/ctrl-(or command+/command- in Mac) to zoom in and out on your screen.
According to the short video below:
Screen Recording 2021-04-30 at 10.35.28 AM.mov