Hm: I may be reading the rules and Meormorph's FAQ differently than you are. In particular, I'm looking at the second question for "The Hours":

Q: What if I can't play anywhere except The Hours, but using a power (such as Shadows) would let me play elsewhere?

A: In this case, you may either:
- Not use the power, and play on The Hours.
- Use the power, and play elsewhere.
You are not required to use the power and play elsewhere. But if you do use the power and now can play elsewhere, you must play elsewhere.
This situation works in reverse, as well. If you currently can play elsewhere, but using a power (such as Shadows) would make it impossible for you to play anywhere except The Hours, you may either:
- Not use the power, and play elsewhere.
- Use the power, and play on The Hours.

But here, after you use Shadows ("+1"), you still have a valid play; you can put the 6 on The Rider ("Unique"), which makes the unplayed 7 become an 8 for the rest of the turn. The way that I read that FAQ entry, the game is correct not to let you play on The Hours in that situation.

On the UI front, what you're suggesting is actually how I was initially thinking of implementing Shadows. However, that would create some tricky situations, similar to the ones that the last FAQ entry for Shadows discusses ("Q: How does Shadows interact with cards like Dawn or The Noble? A: When you use Shadows, you increment the value of whichever fate you don’t play. This can lead to some tricky scenarios! Let’s walk through a few of them. [...]").

For example, what would happen if you had two fates, A and B, and you explicitly chose to apply the +1 power to A, and that left you unable to play anywhere except The Hours? We'd need to ensure that, if playing Shadows on B would let you play somewhere other than The Hours, we prevented you from playing on The Hours and let you switch to the other token.

Instead, the way the game works is a lot more similar to what that FAQ describes---the token you don't play does not get the +1 effect until you play the other one! When you have the Shadows power active, instead of asking "Would either of fates A and B be valid on this card?", the game asks "If I had fates A and B+1, would fate A be a valid play? If I had fates A+1 and B, would B be a valid play?"

Does that make sense? Am I understanding what you said correctly?

I went and took a closer look at your replay, and I saw what you were originally talking about. It turns out that there is a bug specific to The Stranger ("Odd") that is causing it to ignore the effects of Shadows ("+1") for the purposes of determining which fates can be played.

If we imagine that that bug has been fixed (and it has been; the fix will be included in my next release) I think that the game is correct that in showing that playing a 6 on The Rider ("Unique") is your only valid play.

You had a 6 and 7 in hand, and there were a 1 and 2 in play. If you play your 6 on The Rider, the 7 in your hand becomes an 8, and that satisfies the uniqueness rule; but if you play the 7, the 6 in your hand becomes a 7, and that then the uniqueness rule is no longer satisfied.

What I was trying to explain in my previous comment is that, if I'm reading the rules correctly (in particular the FAQ entry on Shadows), you can't pick which fate you want the +1 power to apply to in advance in order to create a situation where you can play one fate on The Hours, if you could play the other fate on another card. My reading is that Shadows *always* applies to whichever you don't play.

Does that make more sense? Maybe I'll create a post on BGG and see if we can get one of the designers to weigh in.

I recently got a response from one of the designers about this (in this BGG thread: boardgamegeek.com/thread/3306166) and I still think that my interpretation is correct and matches his, so I'm going to mark this "notabug", but I'll keep an eye on that thread and if the designer comes back and tells me I'm wrong, we'll change this!