diff --git a/app/assets/javascripts/discourse/app/lib/autocomplete.js b/app/assets/javascripts/discourse/app/lib/autocomplete.js
index f08ac17ee9d..202d8d4385e 100644
--- a/app/assets/javascripts/discourse/app/lib/autocomplete.js
+++ b/app/assets/javascripts/discourse/app/lib/autocomplete.js
@@ -94,6 +94,19 @@ export default function (options) {
   let div = null;
   let prevTerm = null;
 
+  // By default, when the autcomplete popup is rendered it has the
+  // first suggestion 'selected', and pressing enter key inserts
+  // the first suggestion into the input box.
+  // If you want to stop that behavior, i.e. have the popup renders
+  // with no suggestions selected, set the `autoSelectFirstSuggestion`
+  // option to false.
+  // With this option set to false, users will have to select
+  // a suggestion via the up/down arrow keys and then press enter
+  // to insert it.
+  if (!("autoSelectFirstSuggestion" in options)) {
+    options.autoSelectFirstSuggestion = true;
+  }
+
   // input is handled differently
   const isInput = me[0].tagName === "INPUT" && !options.treatAsTextarea;
   let inputSelectedItems = [];
@@ -187,7 +200,11 @@ export default function (options) {
             " " +
             text.substring(completeEnd + 1, text.length);
           me.val(text);
-          setCaretPosition(me[0], completeStart + 1 + term.length);
+          let newCaretPos = completeStart + 1 + term.length;
+          if (options.key) {
+            newCaretPos++;
+          }
+          setCaretPosition(me[0], newCaretPos);
 
           if (options && options.afterComplete) {
             options.afterComplete(text);
@@ -276,8 +293,12 @@ export default function (options) {
     div = $(options.template({ options: autocompleteOptions }));
 
     let ul = div.find("ul");
-    selectedOption = 0;
-    markSelected();
+    if (options.autoSelectFirstSuggestion) {
+      selectedOption = 0;
+      markSelected();
+    } else {
+      selectedOption = -1;
+    }
     ul.find("li").click(function () {
       selectedOption = ul.find("li").index(this);
       completeTerm(autocompleteOptions[selectedOption]);
@@ -549,8 +570,8 @@ export default function (options) {
       // Keyboard codes! So 80's.
       switch (e.which) {
         case keys.enter:
-        case keys.tab:
           if (!autocompleteOptions) {
+            closeAutocomplete();
             return true;
           }
           if (
@@ -583,6 +604,7 @@ export default function (options) {
           markSelected();
           return false;
         case keys.backSpace:
+          autocompleteOptions = null;
           completeEnd = cp;
           cp--;
 
@@ -606,6 +628,7 @@ export default function (options) {
           updateAutoComplete(dataSource(term, options));
           return true;
         default:
+          autocompleteOptions = null;
           completeEnd = cp;
           return true;
       }
diff --git a/app/assets/javascripts/discourse/app/lib/search.js b/app/assets/javascripts/discourse/app/lib/search.js
index 0b0f9ecb2f6..e5b2002f0b9 100644
--- a/app/assets/javascripts/discourse/app/lib/search.js
+++ b/app/assets/javascripts/discourse/app/lib/search.js
@@ -220,6 +220,7 @@ export function applySearchAutocomplete(
         key: "#",
         width: "100%",
         treatAsTextarea: true,
+        autoSelectFirstSuggestion: false,
         transformComplete(obj) {
           return obj.text;
         },
@@ -240,6 +241,7 @@ export function applySearchAutocomplete(
           key: "@",
           width: "100%",
           treatAsTextarea: true,
+          autoSelectFirstSuggestion: false,
           transformComplete: (v) => v.username || v.name,
           dataSource: (term) => userSearch({ term, includeGroups: true }),
           afterComplete,