Changes to the summary show up on the board history, but not topic history:
See summary actions for https://www.mediawiki.org/wiki/Topic:Sbwqem7y14204dxe ("What is ofeiwefweowf?") and history pages https://www.mediawiki.org/w/index.php?title=Talk:Sandbox&action=history and https://www.mediawiki.org/w/index.php?title=Topic:Sbwqem7y14204dxe&action=history .
The actions took place on 2015-02-20.
On the board history, they show as:
(cur prev topic) 18:54, February 20, 2015 . . Mattflaschen (WMF) (talk | contribs) edited topic summary on What is ofeiwefweowf? . . (+9) (cur prev topic) 18:54, February 20, 2015 . . Mattflaschen (WMF) (talk | contribs) created topic summary on What is ofeiwefweowf? . . (+12)