This didn't happen, but a player posed me this question in my last tournament.

"If it's the first the game in a round and by turn 2 I draw a card that I know is in my SB. I call the judge and ask him to speak with him away from the table. I know it's a GL and I'm OK with it. Can I ask you to write the penalty on the slip only at the end of the match so I do not give my opponent any kind of advantage? I'll concede the game right away, so the result will be the same."

So, to make things clear, player accepts GL but asks not to write it down on slip nor to inform opp of anything because he thinks it might give information on opponent on the nature. I'm actually divided on this one.

I cannot figure out which information player doesn't want to give away. Honest.

What's the problem with the opponent grabbing the slip and reading something like “D/DLP - failed to desideboard”?

First, I would need to find out from the player what sort of advantage he
is concerned about. As long as we aren't informing the opponent of the
name of the cards that were illegal, I see no advantage that could be
gained.
Second, I would be wary of any player who didn't want the opponent to know
why they got a penalty. They could be trying to avoid the opponent
appealing the ruling or sharing additional information that may lead to an
investigation.

Hi Luís,

I'm wanna be sure I understand the player's request here. What is it they
are trying to avoid?

It sounds to me they're afraid that I'll write the actual card they failed
to de-sideboard on the slip? That is easily solved by me just writing
“failed to de-sideboard”.

If that's not the case, they'd need to present me with a very convincing
explanation on what advantage the opp. get from knowing the player received
a GL.

Regardless, I would not accommodate the request to not have the opp. know
what's happening. Everyone else is subject to this.

Den 15 nov 2016 16:57 skrev “Luís Guimarãis” <

You don't have to write that AP drew “card name” just write in the entry
slip he drew a sideboard card.​ That doesn't provide any relevant info to
the opponent he might want to hide like the “card name”. But we have to
register the infraction and its penalty.

I think it's worth finding out if this player is concerned that you'll write the name of the card on the slip (which you can assure them you won't) or if there's another reason. Maybe the player wants his or her opponent to think that he or she conceded because he or she had a near-unwinnable game one, and conceded to conceal which deck he or she was playing. Maybe the player is concerned about getting witch-hunted for “cheating” by Reddit. Maybe this player just feels really embarrassed by their error and doesn't want their friends to make fun of them for getting penalized.

Regardless of the reason, however, I cannot think of any reason why I would honor this request. In addition to the issue Shawn pointed out (the opponent might have some information to bring to light that would make you re-consider whether this really was an accident), I have a logistical concern: I might forget to actually write it. If we're at the very beginning of the round, I have to remember to keep an eye out for this slip to finish and grab it before heading up, or fish it out of the stack of slips later and hand it back to the scorekeeper to enter a penalty, or write down a bunch of details, then walk up to the scorekeeper now with a dedicated penalty slip, at a time when floor coverage is probably light due to deck checks.

That said, I don't think I've ever heard of this actually happening at an event.

Originally posted by Luís Guimarãis:

This didn't happen, but

I almost stopped reading at that point (heh)…

…but this is worth addressing:

Originally posted by Luís Guimarãis:

player accepts GL but asks not to write it down on slip nor to inform opp of anything because he thinks it might give information

Short version: No.

As others have said, it's a basic (and hopefully obvious) principle of judging, we don't include details in the description that would give opponents any information. I can't imagine any other (valid) reason for the player to request this - but I can imagine one reason to request it: hoping we'll forget to record the penalty later. (That's actually a very real possibility, which is why it's important we write it down ASAP, before we get distracted by the next judge call.)

If a player doesn't want a penalty recorded, it's worth finding out why - again, as others have said. However, my reason for wanting to find out why is to see if there are other concerns. Perhaps that player had a similar penalty in an earlier round, and he's worried it'll get worse the 2nd time. Perhaps that player has a history of this mistake, and he's worried it'll look suspicious. And maybe it is suspicious (least likely, but we'll never know if we don't ask.)

d:^D

The penalty should be written down right away, and the player assured that you won't write the name of the offending card.

(Note that not writing the name of offending cards is only done when the card isn't known to both players. If someone goofs up by targeting a creature with hexproof, or something, it's absolutely fine to write the names of the cards involved, and you should, as it's better information in the event a pattern of behaviour emerges.)