It came up in a course I was doing on studying pro games, so may as well pass on some knowledge 
A little bit more about that game in particular
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This is a joseki. That means that both players played (nearly) optimal moves:
The joseki is finished now. That means that (for the time being) it’s optimal for both players to tenuki.
Black correctly played tenuki after 10, and then white decided to play hane & connect:
This is not optimal play by white, so it’s not joseki. The AI thinks white lost 2 points from this little exchange. That qualifies as a mistake by strong player standards. Joseki dictionaries can’t possibly cover all conceivable mistaken post-joseki variations, so they don’t.
You’re basically on your own once the joseki has finished.
But the fact that white’s moves 1 & 3 in the 2nd diagram are suboptimal, doesn’t mean that black’s optimal response is still tenuki. It’s not as if white’s moves accomplish nothing. They do increase the urgency for both players to play at D10 and/or H18.
The AI thinks black’s best response is a double-purpose move at D10 to deny white’s extension from their strengthened wall (creating a fairly solid white moyo in the upper left) and create a black moyo in the lower left, while a close second is black crawling at H18 to deny white’s now painful forcing move at H18 that would increase white’s moyo potential in the upper right.
However both players keep ignoring those good moves D10 and H18 (to the AI’s chagrin).
Although ~10 moves later black does take D10, the game ends (~50 moves after that) without H18 being taken by either player.
Either way, missing the optimal/blue moves is not a big deal when you’re still playing good alternatives that are worse only by ~1 point or less.
Such minor opening mistakes probably won’t affect the game result at your level (this game remained pretty close until move 76). They tend to be small compared to middle game mistakes (like in this game moves 77, 79, 83, 87, 88 and 91).
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Thank you for your analysis
Btw: is there a built-in way to add diagrams if your games?
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I don’t think you can add dia. in your games. I mean in an easy way. You can reproduce them on demo boards and then link the demo, maybe something like this.
Sorry, should have read “of your games”.
I mean simply an image of a position like in your post. With a complete game a can easily create a link, but with a position I need to snapshot and upload again?
Well to post here I use a demo, screenshot, edit if needed (mostly crop tool) and upload the final image here yes.
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There’s a button called link to game (on the sidebar on desktop, under the board on mobile)
https://online-go.com/api/v1/games/73092158/png/73092158.png
^latest /end position png exists.
Then there’s a way to make an animation also.
but it can be a “one-move animation”.
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Now that’s great