Seems that "§ion=0" works inconsistently between "&action=raw" and "&action=edit"
According to the manual
"§ion=0" should return the first section (introduction) only, and does so for other &action's, such as &action=edit. But for &action=raw it returns not the first section, but the entire article markup.
Confirmed on MediaWiki-General:
<RoanKattouw> FT2: action=edit§ion=0 behaves as expected: confirmed
<RoanKattouw> action=raw§ion=0 returns entire page: confirmed as well
<RoanKattouw> The entire article, all sections
<RoanKattouw> I suggest you go ahead and file ;)
(slight cleanup to irc for readability; quoted with permission)