6 words - not counting reminder text.
Being tapped is pretty much the same thing as "can't block" anyway.

Shame it can't quite be "Tap two creatures". Oooh! Could it be "Tap two targets"? That even alliterates better!

I don't know about the ambiguous 'targets' wording, but...

Oh no. Now it should have the reminder text about what is a 'permanent' (see Nature's Spiral).

Much better than the targeted versions by avoiding any "up to" business as well.

While I generally have no problem with tapping at sorcery speed in red, it should be noted that with instant-speed removed from common the speed is no longer a good distinguishing feature for colors, so you don't want to overdo the innovation with regards to the color pie.

I can see the point about non-instant tapping no longer being a real option. Still, IMO sorcery speed tapping isn't particularly nor since it can only be used aggressively. Plus, I used tapping instead of "can't block this" to showcase the tap reminder text. Learning/understanding this aspect of being tapped is nice so I would prefer using it where possible. In limited, I think this will have at least a 90 % chance of meaning the same thing as "creatures you don't control can't block this turn".

I don't see what's wrong with aggressive tapping in white or blue. Blue makes stuff unblockable as well. I think we can make use of the "doesn't untap" version for them though, so it can be defensive as well?

Now that I really think about, yeah, fair enough.