Merge pull request #2305 from awesomerobot/master

some adjustments for the username relocation...
BUGFIX: improve alignment
BUGFIX: merge played up correct visual styles
BUGFIX: styling
change "Log In" to "Sign In"

because
http://www.designcult.org/2011/08/why-do-we-call-in-logging-in.html
copyedit to explain reply rule
minor copyedits on flagging
some alignment fixes for the new username position