Improve comments

Author: vy

log4j-core/src/main/java/org/apache/logging/log4j/core/pattern/ThrowableStackTraceRenderer.java

@@ -268,7 +268,11 @@ static final class Metadata {
             final int stackLength;
 
             /**
-             * The stack trace of this {@link Throwable}
+             * The stack trace of this {@link Throwable}.
+             * This needs to be captured separately since {@link Throwable#getStackTrace()} can change.
+             *
+             * @see <a href="https://github.com/apache/logging-log4j2/issues/3940">#3940</a>
+             * @see <a href="https://github.com/apache/logging-log4j2/pull/3955">#3955</a>
              */
             final StackTraceElement[] stackTrace;