If I wonna use a character ability, the character must be stand, even if the ability doesn't require the kneeling? For example with the orphan of the greenblood, can I use his ability even when he is knelt??

I don't think so, I don't read this rule anywhere, but my friend said me and I want to be sure.

Thank youuu

Frankytail said:

You can use any triggered or passive ability/effect as long as the cost is paid for. If the character must kneel to trigger it's own ability, then it must be standing in order for you to kneel it to pay the cost. Otherwise, as long as you can pay the cost, then the character does not have to be standing in order to use the ability.

So, for your Orphan of Greenblood example, you can still trigger his ability even if he is knelt because discarding him from play is the only cost for his ability.

Wouldn't your friend have played L5R by any chance?