New guidelines regarding characters and strings

I will say out multiple possible guidelines, might have gotten some wrong, because not reading with care. But all you can improve them or discard. Under portability I also mean some sort of direct communication between two programs on two different platform.

1. Use Unicode ( u8"", u"" and U"") instead of implementation defined( "" and L"") characters and strings
   Reason: Portability.
2. Don´t compare characters of different type with each other.
   Reason: They are likely to have different values.
3. Don´t compare u8"" and "" strings between each other.
   Reason: They might not be same.
4. Don´t compare signed, unsigned and plain characters and strings with each other.
   Reason: They might not be same.
5. Prefer to use same type of character and string for one project
   Reason: Its easy to accidentally mix them up.
6. Prefer to have characters unsigned?
   Reason: Portability. Plain char is implementation defined.
7. Don't use byte/single character based string manipulations on variable length encodings like UTF-8, UTF-16.
   Exception: UTF-32 as it is fixed-length?
   Reason: Letter might be combination of multiple characters.
8. Care with endianness for UTF-16 and UTF-32?
   Reason: Portability