From my ticket SSP-49823 "Can't navigate from pullrequest commit to commit page":

In Bitbucket 5 I can easily navigate from within a pullrequest's commit to the commit detailed page by clicking (1) and (2).
But in Bitbucket 7.6 I can't. I would appreciate to re-implement this.

As stated in SSP-49823, the solution today is to search for the commit by commit-id in the global search. But in my opinion this is a regression.