Complex sentence: There is no clearly defined Markdown standard, apart from the original writeup and implementation by John Gruber, which is considered to be abandonware, leading to fragmentation as different vendors write their own variants of the language to correct flaws or add missing features.
Split into simpler sentences: There is no clearly defined Markdown standard, apart from the original writeup and implementation by John Gruber, which some consider to be abandonware. This has led to fragmentation as different vendors write their own variants of the language to correct flaws or add missing features.