In the first meeting of Dumbledore's Army at the Hog's Head Hermione asks the students present to sign a parchment, which they all do. The parchment serves as a magical contract:

When the last person — Zacharias — had signed, Hermione took the parchment back and slipped it carefully into her bag. There was an odd feeling in the group now. It was as though they had just signed some kind of contract. ~ Harry Potter and the Order of the Phoenix

The parchment had a jinx on it, whose purpose was to serve as a warning they were betrayed:

Hermione’s eyes slid rapidly down the notice. Her expression became stony. “Someone must have blabbed to her!” Ron said angrily. ... “No, they can’t have done because I put a jinx on that piece of parchment we all signed,” said Hermione grimly. “Believe me, if anyone’s run off and told Umbridge, we’ll know exactly who they are and they will really regret it.” “What’ll happen to them?” said Ron eagerly. “Well, put it this way,” said Hermione, “it’ll make Eloise Midgen’s acne look like a couple of cute freckles.” ~ Harry Potter and the Order of the Phoenix

As we know, when Marietta betrayed the DA she'd SNEAK written all over her face among other unpleasant cosmetical changes.

I had the impression that a few people in the first meeting weren't that thrilled by the idea of the DA and only joined because of peer pressure, like Zacharias Smith, Ernie and Marietta, who was clearly intimidated by Umbridge and wasn't really secret group material. Why not allow people like her to leave the group, warning them only that if they'll disclose the secret they'll be jinxed?

Wouldn't it have been better tactics to tell the DA members about the jinx, to deter them from breaking the magical contract as it is done in the case of the unbreakable vow and the one that's placed on the Goblet of Fire?

After all, Hermione must have studied magical contracts and the jinxes connected to them to do her parchment jinx to get an idea how it's usually done.

closed as primarily opinion-based by Himarm, Skooba, user13267, Valorum, Dave Johnson Nov 4 '16 at 20:53

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

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    It's reasonable to assume that a forewarned snitch would be forearmed and could, with a full wizard's help, evade the jinx. ("I'll tell you stuff you want to know if you snip the Jinx that's on me..."). Alas, no canon to support or erode this theory. – gowenfawr Nov 3 '16 at 14:18
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    People like and trust Harry, and that's a big part of the DA's success. If Hermione came out and told everybody that they had been tricked into magically committing themselves to secrecy, that would lead to resentment and make it harder for Harry to earn the group's respect and loyalty. Hermione would know that Harry is basically incapable of being a "keep people in line with fear" sort of leader, and wouldn't want to undermine him with any overt use of threats/coercion. – Charles_F Nov 3 '16 at 14:47
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    @CharlesFrayne but wouldn't that happen anyway when the jinx activates? Cho, for one was wery pissed about it. – user68762 Nov 3 '16 at 14:54
  • This seems very opinion-based. Certainly there's no canonical reason given – Valorum Nov 3 '16 at 14:56
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    @R.Skeeter It did happen eventually, but it happened after Harry had had time to establish himself, which made it less damaging.And it wasn't necessarily guaranteed that it was going to happen. If the jinx only comes to light after everybody can see that it was justified, that's better than everybody thinking from the start that they're not trusted. And if it never came to light at all, that would be ideal. – Charles_F Nov 3 '16 at 15:17

Just from what we've seen of Zacharias Smith's character, as well as Marietta, Ernie Macmillan, etc., it seems like Hermione made the right choice. If she had told everyone before they signed it about the jinx, one of them would invariably have not signed the contract and told Umbridge. probably Zacharias. If she waited until after and told them, they might not have told Umbridge--so they could avoid making their faces any worse, if possible, but they would've almost definitely quit the DA and antagonized Hermione and Harry. Fred and George would try to trick someone into telling Umbridge. Obviously Hermione didn't want this, so she chose not to tell anyone.

Unfortunately, you might say, this didn't work; one of them, Marietta, did tell on the DA. Why didn't Hermione force this? Now, of course, we must immerse ourselves fully into the realm of guesswork. Based on Hermione's character, it is probable that she assumed that the contract was binding and that such people would never go back on their words, or simply that they were too good to submit to the pressure of Umbridge. Either that or she correctly guessed that it was only a matter of time before one of them told--but that telling them would simply make Marietta angrier, causing her to tell earlier. Or that Zacharias Smith correctly assumed that it would make his face look better to have "SNEAK" written on it.

There is no canon I can find to support any of this, but it seems pretty plausible.

  • There are a lot of good points here, except i am not sure Forge would do this for the sake of a joke. I can totally see them egg on a drunk slytherin like Montague to make an unbreakable vow to fly to the moon, but not this. – user68762 Nov 3 '16 at 15:23
  • @R.Skeeter I could see it possibly if some kind of joke went too far or something. Or maybe if they taunted Zacharias so much that he did it in anger. Something like that – CHEESE Nov 3 '16 at 15:26
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    +1 for talking smack about Zacharias – MissMonicaE Nov 3 '16 at 16:10

Because a jinx can be undone, and this is probably a very specific jinx (so there is probably a known counterspell). Hermione is a very good wizard but she was still in her fifth year, so the chances that what she did is easy to dispel are high.

A wizard like Dolores Umbridge would probably have been able to prevent the jinx's effect from triggering, or to completely dispel it, or at least to find someone who could do that. The only way of keeping it effective is not telling anyone that the jinx exists, so that it can properly trigger if and when the betrayal happens.

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    You overestimated Umbridge's abilities. It is explicitly stated in the book that she was unable to remove the jinx, and Harry was proud of Hermione for that achievement! – user21820 Apr 11 '18 at 12:40
  • Ok but that is not what I have written :) – AnalysisStudent0414 Apr 13 '18 at 22:43
  • Alright alright. =) – user21820 Apr 14 '18 at 2:33