Clearly, there is something wrong with my understanding of brainfuck, or there's something wrong with bf interpreter on ideone.com.
By entering code as simple as
It appears to work fine, my BF torture test runs properly.
I am NOT going to try to fight this UI to make the BF look correct! It's here: https://github.com/rdebath/Brainfuck/blob/master/bitwidth.b
It does appear to have a large cells size though and isn't fast enough to offset this.
EDIT: (No newlines below Grrr)
Anyway Daniel Christofani's end test:
Gives 'LA' showing that the program accepts input successfully, gives the correct character for newline and gives '-1' for end of file. As it's a big cell interpreter this is perfectly acceptable.