Says whom?
You have to make your post with HTML (there is a drop box above the big text field). This will not work with editing pre-existing posts, but it will work for new ones.
Code tags dont seem to be working correctly, so you might have to quote this post to see the HTML tags.
Code:
test indentation
not indentedtest indentation
not indentedtest indentation
Output:
test indentation with lots of text so that we get a second line. test indentation with lots of text so that we get a second line. test indentation with lots of text so that we get a second line. test indentation with lots of text so that we get a second line. test indentation with lots of text so that we get a second line.
not indented
test indentation
not indented
test indentation
Of course, this requires everything to be on the same line, othwerwise you get lots of extra spacing like:
test indentation
not indented
test indentation