I think it still fine, for the most part the only thing in the gifs that readily spoiled is the reveal of the third eye which like I said the anime already revealed that back in Fishman Island when we switch over to Big Mom, and its clearly Pudding even when you see her in WCI.
Hell even then with the manga and anime you could see people online say it wasn't Pudding there in chapter 651/Anime episode whatever, none of the gifs really show her evil facade in them.
I would still say it doesn't spoil the twist at all, cause the big twist isn't from the third eye.. its the evil facade which again those gif don't spoil and again imo don't leave enough context to guess it.
I mean people from manga readers and anime watches were shocked when the Obito = Tobi reveal happened even when it was extremely obvious before hand, so I would still say it be alright posting a out of context gif isn't to bad to spoil anything.
And even in the OP thread we have a new watcher/reader that so far gets none of the context of what is happening in the arc even if we are more descript and less weary of spoilers there then any thread on the site and it doesn't affect him and he hasn't lost any impact so far and when he will get to those scenes.
It just like with a trailer, you will not really get much until you see the full thing.
I'm just saying I don't think my gifs did much at all to spoil anything, I could have used ones like these to show good faces Oda does:
And spoil the whole thing, Pudding making wacky faces really doesn't spoil evil when she was making faces earlier in the arc:
That and I'm sure even in the old site we (maybe not you but I remember talking to Man God, Jaded (trying to get him into it) and Morlas (those are the ones I remember but I remember more) about it openly so were more considerate now with spoilers.)
But thats just me.