On desktop it is possible to start a new line of text by using Shift+Enter, while simply pressing Enter sends your message.
It seems like same code was implemented on mobile version, making use of same shortcuts, even if they are impossible to use.
How it works now: pressing Enter button on mobile keyboard randomly starts a new line or sends your message. It is impossible to consistently create new lines to make long posts more readable.
How it should work: a separate button for mobile layout that sends message. Enter button on mobile keyboard only creates new lines.
Strangely enough, Wolfery Forum app already uses this feature. A separate button exists there, making it possible to separate this text into multiple small paragraphs.