I more-or-less agree with Brother None's assessment. "Planned" means that it's happening, either because it was already part of the design documentation, or because they're certain they'll include it. "Considering" means "maybe/probably/possibly but perhaps not", depending. "Not planned" means "This game is not designed with bronies and Biodrones in mind, please fuck off".
Why don't we just get the answers from the people doing the replying?
*yawn* Because I was sleeping.
Seriously, I've been doing most of the forum replying lately (I wasn't always, but I am at the moment, and probably will be until I go whining to Kevin, "It's too much work! Make Brother None do it!").
Broadly speaking, your interpretations are correct:
WILL DO = Absolutely will do. (These are usually the things we had in our vision doc to begin with)
PLANNED = Almost certainly will do, but we're in pre-production, so you never know.
CONSIDERING = We have read this idea and it's worth talking about. (Or, like in the case of the MCA idea, it means, "We want this too, but, you know.")
NOT PLANNED = Almost certainly won't do.
WON'T DO = Absolutely won't do. (Again, usually from our vision doc)
So CONSIDERING basically means "not no" (sometimes with a comment to clarify what, exactly, we're considering). For Stretch Goals, it usually means someone in the chain is considering it. For Game Ideas, Colin and Kevin and I will probably look through all the ideas after the KS campaign is over and see what we can/should use.
There are a LOT of good ideas in there, and it's hard to keep up with them all. So sorry if the system isn't perfect.
(I kinda love that parrot).