diff --git a/app/assets/stylesheets/common/base/topic-post.scss b/app/assets/stylesheets/common/base/topic-post.scss
index 2d36cb83463..588eb44e8a2 100644
--- a/app/assets/stylesheets/common/base/topic-post.scss
+++ b/app/assets/stylesheets/common/base/topic-post.scss
@@ -179,7 +179,11 @@ kbd
   margin: 0 .1em;
   padding: .1em .6em;
 
-  * * { display: none; }
+  // don't allow more than 3 nested elements to prevent FF from crashing
+  // cf. http://what.thedailywtf.com/t/nested-elements/7927
+  // 3 levels are needed to prevent highlighted words being hidden
+  // cf. https://meta.discourse.org/t/word-disappears-when-searched-and-in-details-summary-kbd-b/25741
+  * * * { display: none; }
 }
 
 // we assume blockquotes have their own margins, so all blockquotes