Is it possible to remove/replace all javascript from the user postform with HTML <input> only? Or is this brain surgery?

No, it's not. If you know how to switch the JavaScript off in the browser, you could try to do so and you will see that default miniBB form still allows to post a message, just without BB-code buttons and the other JavaScript-related tools.

I suppose, whatever you would need to do, is to remove all related JavaScript codes from the main_post_area.html and main_post_form.html templates.

However I'm not sure why would you need to implement that for all users? Those who have JavaScript disabled, still could post messages. However those who have it enabled (most of users), will make their forum life richer.

Also, miniBB has a lot of message-posting related additions which suppose using of JavaScript by default (for example, Polls, Color selection, Smilies, Preview, Quotes, and all Extra Buttons / BB-codes).

So, I'm not sure I understand the purpose of such request properly...

Thanks that worked, though it took me about a half hour to figure out I needed to do it also in main_topics.html

I'm using MiniBB for use on Sega Dreamcast, a lot of games have internet browsers and one in particular we restored the internet functions for was a really old version that didn't like the Javascript. Java had to be disabled in other versions, so for what I'm using it for I wanted to try removing it and it worked. It actually could even work on the Saturn lol

As for the BB codes, a few of the browsers can copy text, so I'd have to customize it for those commands anyway. Not a big deal
You can see my board at http:bb(d)dreampipe(d)net. Not sure if I can post links I remember there was some filter or something here

Thanks for the quick solution