Staredit (and probably Starforge and StarcraftXtra too) save EVERY string you inset as a seperate one. Even empty ones, if I'm correct.
SCMDraft2 made an attempt to get around this: Suicidal Insanity introduced string recycling into it (dunno if it was done before and by whom, SCMD2 is by far the most prominent example).
SCMD2 string recycling checks wether there are duplicate strings and if there are, it rewrites them so that they are only using up one string as you'd know them.
String unrecycling unlinks strings that are connected by this.
The backdraw is that you have no insight in how SCMD2 handles the strings. I know of one major case (and it happened to me too) where the combination of SCMD2 and other editors caused severe wreckage to the used strings (if the strings are not unliked, both - or all three etc. - change when you change one of them).
I could give you a far more detailed explanation about the way the strings section works, actually. I happen to be the person that brought up a completely new view on the strings section
Out of the common editors (SE, SF, SCMD2, SCXE), only SCMD2 is able do perform string recycling, and as I said, there can be problems when combining it with other editors (This type of string handling is not really backwards compatible to SE & co), which is not necessarily SCMD2's fault. But an option to disable string recycling would be nice, actually