"There are those who'll turn innocent occasions to their advantage" The sentence describes the way Moody works and thinks as an auror. It is part of his job to deal with dark magic and with wizards that have no good intentions. Therefore he is trained to be sceptic and careful around others, and to expect the worst, even though the situation/person/event might seem harmless to others. That's what's meant with "innocent occasion": an event or a situation that seams normal, harmless and not dangerous. In the context of the conversation with Karkaroff the "innocent occasion" he is referring to is Moody's birthday, for which he had gotten a carriage clock as a gift. To others that might seem completely normal and nothing to worry about, because receiving gifts for your birthday is normal, but Moody expected it to be some sort of trap or attack, and thought it might be something dangerous like a disguised basilisk egg. So long story short: Black wizards often try to outsmart others and attack them when it's least expected ( hence " turn innocent occasions to their advantage"). That's what Moody has to be prepared for and that's why he's so mistrustful towards others. I hope I could help you!

Hello! This is an interesting question. I think the original form of the phrase is 'turn something to someone's advantage' which means using or handling something in a way that a person can benefit from it. In this case, that particular 'something' is an 'innocent occasion', like the selection procedure of the champions for the Triwizard Tournament. In my interpretation, what Moody meant to say is that there are people in this world who would use every occasion, even the simplest and most innocent ones, to gain something from them for their own benefit. Moody may have been paranoid, but we do know that whoever altered the goblet of fire, did so in order to capture Harry and use him for their own dark purposes. By saying this, Moody accused Karkaroff for perpetrating this act, obviously because of the latter's past association with the Death Eaters. I hope this explanation will help you to get a better understanding of this phrase.

Hi! So I think in this context, I think that Moody is trying to subtly insult Karakoff by saying that he is taking advantage of Harry’s situation and twisting it to make Harry look bad. Hope that helps! If you have any more questions or want to book a lesson with me for English help, feel free to send me a message!

In this case, Karkaroff is implying that Moody is too suspicious, in a way that isn't normal. She destroyed her birthday present, although there weren't any reasons to think it's something malicious. Karkaroff, thereby, claims that her accusation is unfounded (without evidence). But she replies that there is a point in being suspicious, as even innocent occasions (something that doesn't seem dangerous) could be turned to someone's advantage (used in a way that may put you in trouble and bring benefits to your enemy). Like, Karkaroff may seem innocent but they shouldn't be taken in by him. Hope, it will help))