this is the correct way of allowing // to "comment out" code chunks

pattern$chunk.code = '^/+' will tell the parser to strip // or more slashes from the code chunk; hook.chunk() in knit_hooks is irrelevant here because it is used to render output

R/hooks-asciidoc.R

@@ -37,7 +37,6 @@ render_asciidoc = function() {
     sprintf('+%s+', x)
   }
   hook.chunk = function(x, options) {
-    x = gsub("/{2,}", "", x)
     if (is.null(s = options$indent)) return(x)
     line_prompt(x, prompt = s, continue = s)
   }

R/pattern.R

@@ -43,7 +43,7 @@ all_patterns = list(
                inline.code = ":r:`([^`]+)`"),
 
   `asciidoc` = list(chunk.begin = '^/{2}\\s*begin\\.rcode$',
-                    chunk.end = '^/{2}\\s*end\\.rcode$',
+                    chunk.end = '^/{2}\\s*end\\.rcode$', chunk.code = '^/+',
                     ref.chunk = '^\\s*<<(.+)>>\\s*$',
                     inline.code = '`r +([^`\n]+)\\s*`',
                     inline.comment = '^//.*',