Alt +2, Alt + 1. Without letting go of the alt key. Which is why it was "Alt: 21" (aka. "Alt" index number 21) instead of "Alt + 21" (which would be silly).
While all this "§" stuff is pretty awesome, I would like to point out something else that might be interesting to the modders here. Namely, this: Timmy, Johnny and Spike Timmy, Johnny and Spike Revisited These are articles written by Mark Rosewater, head of Magic: The Gathering R&D. While TCGs and Roguelikes have little in common, Mark's tools for analyzing players are quite relevant to this discussion, and many others that people have in this forum. While I can't remember if he mentions it in these articles particularly, he has confirmed, several times, as an experienced game designer, that the players who really need to be balanced around are Spikes, i.e. people like Essence. For those wondering, I lean heavily towards Johnny, myself, but I know I have attributes of all three. (I can honestly say I know some gamers with no Spike and no Timmy tendencies. I don't really understand either group.) Basically what I'm trying to say is, at least when considering balance, you do have to work with the powergamer in mind.
There are many Alt codes if interested this is a good site explaining them (linked to the list of codes, rather than its home page). though not all of them work in forums too. As for balance on things the best bet is using your own judgement. I was once told with regards to game development is that if you think it is overpowered it likely is, so reduce its power. If it turns out it wasn't overpowered and is now underpowered users are much more apreciative when you increase the power (buff) things than when you decrease power (nerf) it. This is because when you buff it is seen as giving something as opposed to nerfing is seen as taking something away, even if an individual agrees that it is for the better there is still that feeling of having lost something as opposed to having gained something. This doesnt stop things getting through that are overpowered but generally does tend to minimise the cases especially as you get more familure with what you are trying to balance.