Formulating something that can be likened to Fudge Diceless in Play by Post. Considering that, I ask-

Can a thief with terrible ability be described in a great way and be rewarded?

Sure, I don't see why not.

So how can this player/character be rewarded.

The lock probably stay closed, but....?

Depends on how he uses the ability and probably fails.

Perhaps the lock remains, but he's lucky and the actual door falls off? Or perhaps he finds a key nearbye?

There's a bardic PRC that focuses all on luck.

Is the reward for the character or the player describing the thief?

If it's for the character, I'm not sure how or why you would reward it.

If it's for the player, the reward could be in-game benefits like fate points or interesting story situations that come with cool opportunities, such as falling afoul of the authorities and being offered a clean record in exchange for taking on a dangerous task, or a case of mistaken identity with another, more skilled thief.

This reminds me of the story of a half orc thief who intimidates people into not seeing him. I would go with Fate counters so he has good luck elsewhere to pay for all that bad luck. Especially since this sounds like a character made for laughs.

The absolute reverse of the Jedi-mind-trick?

"You no see, you saw nothing, go AWAY!"

This is basically how some gangs apparently work. It's not that they go to a lot of trouble to be stealthy, it's that everyone is too intimidated to admit to being a witness.

One game I was in, ages ago, had a paladin whose player had some of the most consistently bizarre luck with dice...he would routinely score fumble rolls...like, the party gets ambushed and his horse rears--and he tumbles off the horse.  But just about every time he fumbled, the GM would have him roll to see just hiw bad it was...and he would score phenomally well, so much so that he pretty much instantly recovered from the fumble--in the case of the example cited, yeah, he fell off the horse...and landed squareky in his feet, ready to fight.  It happened so consistently that it became a character quirk, and the other characters would get worried if they went into a fight and he hadn't somehow stumbled, tripped, or knocked something over before the fight started.

So, yeah, I think, as a concept, it could work...with the right group.  You'd need a player who could find ways to either salvage failures or make them entertaining (let's face it, if a thief was terrible at thieving, he'd need some way to justify the group keeping him around), and you'd need a group of players that could get the fun out of the character, rather than being frustrated that he was terrible at his job.

RPGuru2 - are you trying to describe the notion of "failing forward"?

Wherein - despite a failure, it does not cause a 'full stop' to play, but, instead opens a new opportunity?

Example: If CharacterA falls off of a roof and hits the ground, they are sure to die.  NPCb pushes CharacterA off of the roof.

- You first 'reward' (fail forward), by realizing - okay, so the Character didn't make any effort to save themselves, but, let's not write'em off just yet.

- You give the player a chance to make a saving throw or some such.
- - Okay, they forgot to cast the spell that would keep them from falling to their death (feather fall)... okay, so let's say CharacterA is not officially falling.

- Character describes that they fall end over end for a moment before letting themselves go feet first, they spot a pole or clothing line, or a awning within arm's reach...
- - Letting them "fail forward", you now grant them another chance catch themselves on said device (who cares that it was never originally described, it's group story telling = it's there now!)

If this is what you are shooting-for with your lock situation:

1) You fail to open the lock, but, in so doing, your foot slipped out of place, and you hear a metallic grating sound under the doormat where you were crouched (lift up mat - reveal key)

2) You fail to open the lock, and now whatever was on the other side is approaching the door (ostensibly to check what's happening on the other side).  Yes, it's still failure, yes, it has a new danger, but, there's still a MEANS of getting through this door.

There's an old Robert Redford movie, The Hot Rock, that describes this sort of thief. Basically, a group of thieves get hired to steal a massive diamond from an African dignitary visiting the US. They mess up -- badly -- and the rest of the movie is them scrambling to undo the damage (and making things worse), while still trying to get their hands on the gem.

Unfortunately, none of the streaming services seem to have it, so the only option right now is a physical copy. Once or twice a month, I ask Netflix to pick it up.

As I started this out with, I am on the trail of reviving an old concept of mine, back around 2005, of creating a diceless collaborative story-telling-but-who-knows-it-be-an-rpg-idea. In my head and experience the closest thing to it is diceless fudge or Amber without the elitism. Something that one could play specifically in play by post, thus, ideally diceless.

The Risus idea of inappropriate cliches is brilliant, and one sees it in Amber rpg, where someone uses perhaps an inappropriate power to get the edge. This is what I am talking about, I am more inclined in pbp to reward the writing than the character. Thus that is why I asked.

Though the half-orc, the quixotic paladin, and the 'B' Team movie all put it in my head that this oooold idea of a story-advanced-game-engine (S.A.G.E.) is possible.

Perhaps the scent of a mod, I am not going to mask what may look like advertising for an interest check some place else. I did put an IC in Game Proposals along the lines of what we are talking about.