Oh look.
Another grammatical moron calling out someone else's lack of grammatical skills.
The word illegible only applies to the actual VISUAL QUALITY of text, not the COMPOSITION of it.
Writing is only illegible due to factors like poor or sloppy handwriting, fading of the ink or other medium in which it was written or printed to the point that it can barely be be seen, extremely small size to the point of requiring magnification, etc, etc.
Once again, the lesson here is: Don't preach at others about that which you are not an expert on yourself.
Have a nice day.