OP, I B T L etc. are general messageboard abreviations, not specific to this one alone.
FIFY - fixed it for you (another general message board abbreviation; used when quoting someone and changing a part of the quote, usually for comedic purposes)
IGH - internally geared hub
DF - diamond frame (the classic bike frame consisting of two adjacent triangles when viewed from the side)
CF - carbon fiber
bent - recumbent bicycle