Someone was breaking a message into small posts because the Submit button got hidden.

"He says later he was writing this on his phone - that is an invitation to frustration. Perhaps, Mr. Ken from Smithfield, you need to find a computer. If you don't want to lose the content (glitches do happen) then compose in a word processing or notepad file first. ---mudelf"

thread.cfm?threadid=56224&messages=32#3974778  

I have this problem myself on a 10" android tablet used in portrait. (chrome browser)(in landscape the keyboard uses 70% of the screen, which I don't like)
Yes, I'll often copy paste from a notepad file.
But the pasted text enlarges the text area down to about the "Mudcat time" line, hiding the Submit button.

The workaround on my tablet is
- 1 - to rotate the tablet to landscape then back to portrait > Submit
or
- 2 - [and I've only just discovered this]
Tap the "Make a link ("blue clicky")" button which is sticking out to the right of the text area ... and the text area gets resized correctly, showing the buttons.

On my 2019 Nokia phone, portrait, the text area gets extended but the Submit \ Preview etc buttons can still be seen and used, albeit that they are amongst the text I'm typing.