Hello danmoller. I'm not sure about the absolute grammatical rule, but "He goes in my house" and "He goes into my house" both sound fine to me.
I'm thinking that the reason it wasn't accepted was that one can also say "He comes in my house" or "He comes into my house"
Nevermind. I just encountered this again and "He comes in my house" was not accepted, but I think that it should be accepted.
I'm not a native English speaker, so I really can't tell, but if your are convinced it's right, use the report error button. They always accept new valid translations we propose.
Using just "em" makes it indefinite, but when it's about "casa", people assume that "em casa" is talking about the house of the referred person. Then, if you say "ele entra em casa", it means: he enters his house.
Also, the word "minha" determines which house is it. Making it unnecessary to use the article.
But in other cases there would be differences:
- Ele entra na padaria = he goes in the bakery
- Ele entra em padaria = he enters bakeries. (indefinite)