Should I use the Arabic Presentation Forms provided in Unicode?

Quick Answer

No. These forms were provided to provide round-trip conversions to legacy encodings, but you should ignore these and use the characters in the main Arabic block for your content.

Doing so means that your content can be understood better by applications, especially when it comes to searching and similar operations.

[I think there are actually one or two characters embedded in the presentation area that are for normal use, but i can't remember what they are at the moment.]

Details