The below is a recent patch from plan9port to acme:
 * https://github.com/9fans/plan9port/commit/8cf52696bed986f8914f214768690d6ca47bae76

It removes superfluous print arguments passed to winevent(...).

<snip>
From: Igor Böhm <igor@9lab.org>
Date: Tue, 05 Oct 2021 09:40:30 +0000
Subject: [PATCH] acme: remove superfluous print arguments (patch from plan9port)

---
diff 6ebb8b9e357944cc29ae3fafc0900ee3e325ed39 956353d6a5034be1df107d195b7808c0da5b367c
--- a/sys/src/cmd/acme/exec.c	Sun Oct  3 17:58:58 2021
+++ b/sys/src/cmd/acme/exec.c	Tue Oct  5 11:40:30 2021
@@ -176,14 +176,14 @@
 		if(n <= EVENTSIZE)
 			winevent(t->w, "%c%d %d %d %d %.*S\n", c, aq0, aq1, f, n, n, r);
 		else
-			winevent(t->w, "%c%d %d %d 0 \n", c, aq0, aq1, f, n);
+			winevent(t->w, "%c%d %d %d 0 \n", c, aq0, aq1, f);
 		if(q0!=aq0 || q1!=aq1){
 			n = q1-q0;
 			bufread(t->file, q0, r, n);
 			if(n <= EVENTSIZE)
 				winevent(t->w, "%c%d %d 0 %d %.*S\n", c, q0, q1, n, n, r);
 			else
-				winevent(t->w, "%c%d %d 0 0 \n", c, q0, q1, n);
+				winevent(t->w, "%c%d %d 0 0 \n", c, q0, q1);
 		}
 		if(a){
 			winevent(t->w, "%c0 0 0 %d %s\n", c, utflen(a), a);
</snap>

Cheers,
Igor