If user is sysop, send a block-sender button back with the

getMailBody data. Use xjs_eval() to render said button.
Added addTwit method. Nothing fancy, just adds your string to
twitlist.cfg and assumes you were really careful about producing
said string and that it won't destroy the universe.

webv4/lib/forum.js

 require('sbbsdefs.js', 'MSG_DELETE');
+require('xjs.js', 'xjs_compile');
 load(settings.web_lib + 'mime-decode.js');
 
 function listGroups() {
@@ -404,10 +405,25 @@ function getMailBody(number) {
     ret.body = formatMessage(pt_body == body ? decoded.body : pt_body); // See above re: pt_body
     ret.inlines = decoded.inlines;
     ret.attachments = decoded.attachments;
+    if (user.is_sysop) {
+        ret.buttons = [
+            format(xjs_eval(settings.web_components + 'twit-button.xjs', true), number, number, header.from, header.from_net_addr),
+        ];
+    }
 
     return ret;
 }
 
+function addTwit(str) {
+    const f = new File(system.ctrl_dir + 'twitlist.cfg');
+    if (!f.open('a')) {
+        log(LOG_ERR, 'Failed to add ' + str + ' to twitlist');
+        return;
+    }
+    f.writeln(str);
+    f.close();
+}
+
 // Returns the user's signature, or an empty String
 function getSignature() {
     var fn = format('%s/user/%04d.sig', system.data_dir, user.number);