TL;DR: You can add stars now!
Note: Colored stars are available, but only I have them at the moment.
Stars on your Flipnotes will not yet show up in your Creator's Room.
I'm planning on a limit of ten yellow stars per person per flipnote.
This feature may not always work. Favoriting, Creator's Room links, and Stars are all dependent on what's left of the old Flipnote Hatena servers, so it may not work perfectly. I'll be fine-tuning it over time.