Sanity check.
I'm clearly missing something.
Try this:
<code c>
int main()
{
printf("hello, world");
return 0;
}
</code>
<code c hello.c>
int main()
{
printf("hello, world");
return 0;
}
</code>
Copying and pasting the first block produces text that is as expected ("unindented").
Copying and pasting the second block produces text that is indented by 4 spaces - every line.
Source code for the second block shows no added spaces in the rendered HTML source.
Help?