Marking the front of your cards

[tutti]

I know I'm not allowed to mark the back of my cards, because that would be obvious cheating. But what about the front of my cards? The mark wouldn't help tell the card apart from any other when viewed from behind.

The reason I'm asking is special energy. The way I like to attach any card to a pokémon is to put it under it, pushed slightly forward to show the title. In some cases this can make it hard to tell special energy from basic ones, so I'd like to put a small mark near the title so I can tell them apart.

I know there are other ways of dealing with this issue, but this way, if allowed, will take the least extra space, which can be a problem at times.

 

[PokePop]

No. This would not be allowed.
They used to allow cards to be autographed and otherwise decorated, as long as it didn't interfere with the text of the card. However, one year, a number of players decided to decorate their card's borders. Some of this spilled over to the edge of the card, effectively marking them when viewed along the side where they were inserted into the sleeve.

There were other reasons as well, but the end result is that you cannot play with cards with any markings on them, front of back. Or side.