From the implementation POV, suckless software is very simple, and this makes it easier not only to tweak configuration (which is usually done C headers through defines), but also any kind of customization you might need.
Take their window manager dwm as an example. The codebase is only 2000 lines long, so any bug you find will have to be hidden in those 2000 lines. If you take a Sunday afternoon to study the code, you will very likely understand how every piece of the software works, at which point you will be in a position to fix anything you might find. You might even end up forking it and implementing your own window manager (AwesomeWM was originally forked from Dwm).
Take their window manager dwm as an example. The codebase is only 2000 lines long, so any bug you find will have to be hidden in those 2000 lines. If you take a Sunday afternoon to study the code, you will very likely understand how every piece of the software works, at which point you will be in a position to fix anything you might find. You might even end up forking it and implementing your own window manager (AwesomeWM was originally forked from Dwm).