This patch modifies backspace behaviour when text is selected so that it doesn't delete the character preceding the selection.
diff 61f028fdacb96dddf66d5ff2edeefc530a00cb58 uncommitted
--- /sys/src/cmd/acme/text.c
+++ /sys/src/cmd/acme/text.c
@@ -680,13 +680,35 @@
 	switch(r){
 	case Kleft:
 		typecommit(t);
-		if(t->q0 > 0)
-			textshow(t, t->q0-1, t->q0-1, TRUE);
+		if(t->q0 > 0) {
+			if(t->q0 != t->q1) {
+				textshow(t, t->q0, t->q0, TRUE);
+			}
+			else {
+				textshow(t, t->q0-1, t->q0-1, TRUE);
+			}
+		}
+		else {
+			if(t->q0 != t->q1) {
+				textshow(t, t->q0, t->q0, TRUE);
+			}
+		}
 		return;
 	case Kright:
 		typecommit(t);
-		if(t->q1 < t->file->nc)
-			textshow(t, t->q1+1, t->q1+1, TRUE);
+		if(t->q1 < t->file->nc) {
+			if(t->q0 != t->q1) {
+				textshow(t, t->q1, t->q1, TRUE);
+			}
+			else {
+				textshow(t, t->q1+1, t->q1+1, TRUE);
+			}
+		}
+		else {
+			if(t->q0 != t->q1) {
+				textshow(t, t->file->nc, t->file->nc, TRUE);
+			}
+		}
 		return;
 	case Kdown:
 		n = t->maxlines/3;