@Tratax No problem!
If you do
renderEffect( frameBuffer, frameBuffer, ... )
Then you are trying to both read from and write to the same texture. Hence, problems! Actually, I'm really glad you asked because this should give you an error, rather than giving the super weird effects that it does.
We'll fix this in a patch of course.
To apply the code highlighting to text, put 3 back ticks above and below the chunk of text you want to make into code. So,
threebackticks ( ` )
loop
repeat
threebackticks