As the title says the question is simple.
I don't understand why in the case of shinjo tatsuos ability you cant target himself if he is participating in a conflict as long as you target a character that is outside and can satisfy the "card must change the state of the game"
While in shameful display case you can target a character that is already dishonored or honored (even if you dont plan to change their status) as long as the other character you target can be dishonored or honored.
I mean in both cases the cost is to target 2 characters. the rest after the "-" is just effect that the only obligation per the rules is that you need to change the game state. Whats the difference between the two wordings that i seem to miss?

Each target needs to be a legal one, and part of being a legal target means that the target can be affected by the ability. Tatsuo's ability says "Move those characters to the battle", if a character can't move in it isn't a legal target. Shameful, on the other hand, says "Honor one and dishonor the other", so when checking for target legality you ask if each target can be honored OR dishonored. Since you check target legality individually, not as a group, if each target can only be honored they are each legal targets, and you can choose both of them for Shameful. The entire difference is that Tatsuo has one possibility for his effect, "Move those characters", while Shameful has two possibilities, "Honor or dishonor".

Shinjo Tetsuo's ability not being able to be used isnt because of a gamestate change, like you mentioned he is changing the game state, it cannot be used because one of the two targets isnt being moved, and the rules state that if something cannot be moved the action cannot happen.

RR Page 11

When an entity moves, it cannot move to its same (current) placement. If there is no valid destination for a move, the move attempt cannot be made.

5 hours ago, yujufrazer said:

Shinjo Tetsuo's ability not being able to be used isnt because of a gamestate change, like you mentioned he is changing the game state, it cannot be used because one of the two targets isnt being moved, and the rules state that if something cannot be moved the action cannot happen.

RR Page 11

When an entity moves, it cannot move to its same (current) placement. If there is no valid destination for a move, the move attempt cannot be made.

I'm afraid that isn't relevant in this case. That he cannot be moved does not inherently invalidate the effect.

Tatsuo's ability targets himself and up to one other. A card may not be targeted if it cannot be affected by an effect. An effect could be used that would move a character already in a conflict, provided that the effect did not target that character and the ability had the potential to change the game state in totality. Only the 'choose' text prevents Tatsuo from using his ability from within a conflict to bring in one other.

2 hours ago, InquisitorM said:

I'm afraid that isn't relevant in this case. That he cannot be moved does not inherently invalidate the effect.

Tatsuo's ability targets himself and up to one other. A card may not be targeted if it cannot be affected by an effect. An effect could be used that would move a character already in a conflict, provided that the effect did not target that character and the ability had the potential to change the game state in totality. Only the 'choose' text prevents Tatsuo from using his ability from within a conflict to bring in one other.

We are stating the same thing, your saying he cannot do his action cause he has to "Choose" him self which is exactly why he cannot do his action when hes already at the battlefield. My bullet point i posted from the rules reference is stating exactly that. He cannot do his effect because he him self cannot be moved. Since

When an entity moves, it cannot move to its same (current) placement . If there is no valid destination for a move, the move attempt cannot be made .

Shinjo Tatsuo's ability cannot be used if he is already participating in a conflict.

The targering requirement is to choose himself and another character, but targets are only eligible if they can be affected by the ability's effects; since Shinjo Tatsuo cannot affect himself, he cannot choose himself as a target, which means that you cannot satisfy targeting requirements, so you cannot attempt to initiate the ability at all.

heres the card ruling. What your saying is that because he cannot target himself he cannot do it, im saying he cannot target him self because he cannot move. Also any effect that would move him with out targeting himself still wouldnt work because of the above bullet point