I have to agree with OddCore - I've read a relatively large amount of the EU and the movie scripts. I've NEVER seen it written as 'OB1' or 'OB1 (KNO-B)' in official literature.
The wikipedia link you provide simply redirects to the main 'Obi-Wan Kenobi' article, common with other commonly misspelled names. The redirect is trivial to set up, and could have been done by anyone at any time, with little to no effort.
Your link in the comment to OddCore's answer (to a google search for "ob1-kenobi") brings up the official Wikipedia article (which doesn't mention that spelling), a facebook page or two, an 'Ewokapedia' article (never heard of that site before), and a hip-hop artist.
I believe what is happening is that someone has an 'epileptic tree theory' (TVTROPES) - a crazy theory that 'MAKES PERFECT SENSE IF YOU JUST THINK ABOUT IT' and has been trying to drum up support for it - adding wikipedia redirects, making minor notes in Wookieepedia articles, etc.
Also, it's worth pointing out that 'Obi-Wan' could have been initially mispronounced 'Ob-Eye wAn (with an 'a' sound like in 'wane')', so it's possible that someone once wrote it as 'OB1' to explain to Mark Hamill how to pronounce it (though it's significantly more likely they just said it once and he picked up on it).