Comments on the copy / wording? 
It replaces the “Log In to Reply” button that is normally there.
Current conditions are:
- entered 5 topics
- read for 15 minutes
- page was loaded 24 hours after the first visit (tech note: this prevents it from ever showing up if localStorage is disabled)
- “Maybe Later” not clicked in the last 24 hours
The 3rd paragraph (these need a lot more copy editing):
sso: "Use your account on the main site to log in."
only_email: "Signing up is easy: you just need a valid email account and a password."
only_other: "Use your %{provider} account to sign up."
one_and_email: "Use your %{provider} account, or an email and password, to sign up."
multiple_no_email: "Choose from any of the %{count} supported login providers to get started."
multiple: "Signing up couldn't be easier: use any of the %{count} available login providers, or sign up with an email and password."