Pluck out some more applicable styles

res/css/views/settings/_JoinRuleSettings.scss

@@ -54,3 +54,35 @@ limitations under the License.
         }
     }
 }
+
+.mx_JoinRuleSettings_radioButton {
+    padding-top: 16px;
+    margin-bottom: 8px;
+
+    .mx_RadioButton_content {
+        margin-left: 14px;
+        font-weight: $font-semi-bold;
+        font-size: $font-15px;
+        line-height: $font-24px;
+        color: $primary-content;
+        display: block;
+    }
+
+    & + span {
+        display: inline-block;
+        margin-left: 34px;
+        margin-bottom: 16px;
+        font-size: $font-15px;
+        line-height: $font-24px;
+        color: $secondary-content;
+
+        & + .mx_RadioButton {
+            border-top: 1px solid $menu-border-color;
+        }
+    }
+}
+
+.mx_JoinRuleSettings_linkButton {
+    padding: 0;
+    font-size: inherit;
+}

res/css/views/settings/tabs/room/_SecurityRoomSettingsTab.scss

@@ -37,37 +37,3 @@ limitations under the License.
     border-bottom: 1px solid $menu-border-color;
     margin-bottom: 32px;
 }
-
-.mx_SecurityRoomSettingsTab_joinRule {
-    .mx_RadioButton {
-        padding-top: 16px;
-        margin-bottom: 8px;
-
-        .mx_RadioButton_content {
-            margin-left: 14px;
-            font-weight: $font-semi-bold;
-            font-size: $font-15px;
-            line-height: $font-24px;
-            color: $primary-content;
-            display: block;
-        }
-    }
-
-    > span {
-        display: inline-block;
-        margin-left: 34px;
-        margin-bottom: 16px;
-        font-size: $font-15px;
-        line-height: $font-24px;
-        color: $secondary-content;
-
-        & + .mx_RadioButton {
-            border-top: 1px solid $menu-border-color;
-        }
-    }
-
-    .mx_AccessibleButton_kind_link {
-        padding: 0;
-        font-size: inherit;
-    }
-}

src/components/views/settings/JoinRuleSettings.tsx

@@ -159,6 +159,7 @@ const JoinRuleSettings = ({ room, promptUpgrade, onError, beforeChange, closeSet
                             disabled={disabled}
                             onClick={onEditRestrictedClick}
                             kind="link"
+                            className="mx_JoinRuleSettings_linkButton"
                         >
                             { sub }
                         </AccessibleButton>,
@@ -286,6 +287,7 @@ const JoinRuleSettings = ({ room, promptUpgrade, onError, beforeChange, closeSet
             onChange={onChange}
             definitions={definitions}
             disabled={disabled}
+            className="mx_JoinRuleSettings_radioButton"
         />
     );
 };