ctrl-A/ctrl-E are the home/end emacs/bash/etc. shortcuts.
In a multiline field, ctrl-A sends the cursor to the beginning of the current line, but ctrl-E sends the cursor to the end of the entire field.
Probably, ctrl-E should match ctrl-A's behavior (end of current line), but they should at least be symmetrical.
This appears to be a bug in OS X only. I am looking into this.
Fixed in commit 8fba70b.