The bot's understanding of simple phrases such as "you are nice" comes from the NounVerbAdjective script. This script will understand and remember persistently simple facts, or answer simple questions.
you: The sky is blue
bot: Ok, the sky is blue.
you: Is the sky blue?
bot: Yes, the sky is blue.
The bot will now know that #sky is related to #blue by #is. It stores this in its database (brain), and will be able to answer this in any future sessions.
You can disable these types of responses by removing the NounVerbAdjective script from the Scripts page under Admin.
When the bot constructs scripted responses it will use its knowledge of grammar for replacing "you" with "I" and "are" with "am". It actually learns grammar from its conversations, so will choose whatever word "sounds" correct similar to a human.
So, if it says "Ok, me am nuts", you can train it with the phrase "Ok, I am nuts", then it will learn the correct grammar. Technically, training with "I am nuts" should be sufficient, but the bot's have some issues with "you" currently because it is both subjective and objective.
Learning grammar can work both ways, if users constantly use bad grammar, it can learn bad grammar as well.