Por quê nao é "com o Luis"? sempre pensei que o articulo é necesário com os nomes em português
It is not necessary
I think you're right.
Luiz is not wrong, it's a parental choice. I am friends with a Brazilian named Luiz.
Louis should be an acceptable typo of Luis!
Its the name of a person so you shouldnt need to change it.
No, but since we don't know how she is spelling it...
Even more so, Luiz should surely be accepted.
As far as my limited understanding goes, one can use the definite articles for names as well, although it is not necessary. However, is this true as well when certain prepositions (like 'com', in this case) precede the name?
It is true, and also with prepositions like "com" you can choose to use the article or not.
I accidentally put "jog". I'm positive the explanation is self-explanatory.