I can't think of pen-and-paper game that uses a system like this, though even AD&D encouraged DM's to suggest to players to change the alignment if they seem to really be acting outside their alignment. Some of the White Wolf games also track alignment by points, but the path(s), like Humanity, are still normally chosen and laid out ahead of time. Probably the closest is the old Star Wars RPG that carefully tracked dark side points and declared that a character had gone over to the darkside after receiving too many of them.
Video games do this frequently though. Infamous used it, and many Star Wars based games let you choose Light v. Dark entirely based on actions.
Ambiguities and Justifications
But, as others have pointed out, you'll run into the question of what constitutes evil. Look at the examples you gave. In the first case, you have the daughter being seduced. Now, if she was already a part owner of the potion selling shop, then seducing her and asking for a potion isn't necessarily evil, its more neutral...The character had a pleasant night of passion with another character looking for the same and received a gift from his new lover afterwards, that is neither good nor evil. At least not to a liberal Western attitude...In certain more conservative, fundamentalist societies seducing her without marrying her could merit more than one evil point and could lead to one or both of them being executed.
Similarly with the kobolds, it may have been a very kind, generous, and good act to save them...Unless you are using the trope, common in many fantasy works, that kobolds are almost universally evil. In that case, there might be a bounty for killing them. Saving them might then actually be an evil act. Or the middle ground is saving them could be an act of mercy, but an illegal one so they would get both a good point and a chaos point....
In short, if you want a system like that you may want to make it more objective. There are a number of ways of doing this:
Set up a code that is at least somewhat independent of good or evil. Light v. Dark in Star Wars is deliberately tied to morality to a degree, but only a degree. A dispassionate light jedi can calmly do evil acts (and do in cannon! In The Clone Wars annimated series in particular the Jedi often take actions that at least require an "ends justify the means" atitude if they aren't downright evil). In Vampire, most Vampires with high Humanity will be good, but its more about compassion and control than good per se. So you can wind up with evil vampires with high humanity and good but reckless ones with low humanity.
When you see an action with moral implications, flat out ask the player how they view their action and let that be highly influential, if not the final word. This lets intentions shine through and minimizes debate.
Make it about reputation instead of real alignment. Then its not a matter of "I acted this way, so I am this." Its a matter of "I acted this way, so everyone sees me as this." This takes intention entirely out of it, and also makes it less personal. You avoid questions of what is good and instead are asking about how the populace with their particular culture views the acts. It also avoids arguments about, "What do you mean I'm evil? I was playing good, everything I did was justified!" (Or the reverse, "I'm not good. It just so happened that in every situation the most profitable action also helped other people. I'll stab Joey in the back right now if it would advance my goals, it just hasn't yet!") Of course it does open up questions about witnesses and how everyone knows, but there are various ways of handwaving that.