Problem: Collapsing "Advanced Settings for Email Aliases" section hides error messages.
This has to do with setting an Email Alias (from the Account settings page). This is an offshoot of other recent discussions (here and here) but is a different issue.
Currently, the user has to click on "Advanced Settings for Email Aliases" in order to expose the Email Alias data entry field. Once they make an entry and click on "+Add Email Alias" the section immediately returns to its collapsed state, leaving no visible indication of success or error. Collapsing this section and hiding an error message is unexpected behavior.
Lacking any indication of an error, the unsuspecting user will most naturally assume that their entry was accepted and move on. If their entry was not accepted for some reason, the user cannot see the resulting error message unless they know to re-expand the section. Otherwise, they inevitably will be frustrated when they can't post a message from their "new" Email Alias.
Suggestion: Remove the expand/collapse control from the "Advanced Settings for Email Aliases" section, leaving it in its expanded state by default. Error/success messages should always show after the user makes a change. This should not be a problem given that the section's description and instructions are already quite clear.