Snape could be in great danger. Voldemort might immediately try to kill him. Snape would have to fight for his life or try to escape. His status among the Death Eaters would be completely ruined, and he'd become a hunted man.
The consequences are quite severe. Firstly, Voldemort would no longer trust Snape, which is a huge blow as Snape has been working undercover for a long time. He may face torture from Voldemort to extract more information about the Order of the Phoenix. Also, his position at Hogwarts would be compromised. He might be forced to flee Hogwarts, leaving behind his students and his double - agent work there. And his relationship with the other characters in the wizarding world would be forever changed, with many either fearing him more or seeing him as a traitor depending on their allegiance.
There are many ways this could happen in fanfic. One way is that Harry uses his connection with Voldemort's mind. Since Harry has a link to Voldemort's thoughts, he might be able to pick up on Voldemort's doubts about Snape. And then Harry starts to investigate Snape further. He might recall some strange actions of Snape in the past, like his ambiguous loyalty during certain battles or his secret meetings with some unknown figures. Combining all these, Harry eventually realizes that Snape is a spy.
In a fanfiction scenario, Harry's actions could cause a complete breakdown in any potential for a positive relationship between them. Snape's loyalty to Dumbledore and his role in protecting Harry from the shadows would be put at risk. Harry would have to face the fact that he may have made a huge mistake. And Snape, who has sacrificed so much already, would be in an even more precarious position, both with Voldemort and in the wizarding world in general. This could lead to a chain of events that completely alters the course of the wizarding war, with far - reaching consequences for both Harry and Snape.
Snape might be given a warning by Dumbledore at first. Just a simple 'stop this behavior or else' kind of warning.
One possible plot could be that Voldemort initially doesn't believe Harry. He might think it's a ploy by Harry to create discord among his Death Eaters. But then he starts to suspect Snape when he recalls some of Snape's past actions that seem a bit off in the context of loyalty to him.
Harry might become more determined to prove Snape wrong. He's a stubborn character, and Snape's yelling could fuel his desire to show that he's not the misbehaving student Snape seems to think he is.
Yes, there are some fanfictions with such out - of - the - box concepts in the Harry Potter fanfiction community. However, these are not in line with the original story's canon.
One possible reason could be that Snape fails to deliver crucial information. Voldemort is a very demanding and unforgiving master. If Snape doesn't give him accurate details about the Order of the Phoenix's plans, for example, Voldemort would surely be enraged and punish him.
Yes, it could be possible in fanfiction. Fanfiction allows for wild reinterpretations of the source material. Maybe there could be a story where a dark wizard in the past manipulated their family trees so that Harry, Snape and Voldemort are unknowingly brothers. It would make for a very interesting plot, full of drama and conflict as they are on different sides in the original story.
Well, one possible consequence could be detention. Snape is strict and would likely punish Harry for breaking school rules by smoking. He might make Harry clean the Potions classroom or do some other unpleasant chore.
Snape might endure the punishment in stoic silence. He is a complex character and often used to hiding his true emotions. So, he could just grit his teeth and bear it, all the while plotting his revenge or a way to get out of the situation.