Assertion:
INS and DEL can be nested. Because the only visual difference is strike and underline, only simple nesting will have any visual effect. Nesting INS within INS, for example, will look no different from a single INS element occurrence. Nesting INS within DEL however will produce the necessary feedback.

Simple INS example:
filler text ins text filler text

Simple DEL example:
filler text del text filler text

INS nested inside INS example:
filler text ins1 ins2 ins1 filler text

DEL nested inside DEL example:
filler text del1 del2 del1 filler text

DEL nested inside INS example:
filler text ins1 del2 ins1 filler text

INS nested inside DEL example:
filler text del1 ins2 del1 filler text