I do think this is mostly a UI problem. As someone else suggested in this thread sites like GitHub which show only a linear list of commits should probably default to something more like `git log --first-parent`.

There also sounds like a need for `git bisect` to be smarter about DAG traversal, in that it seems to treat the branch as if it were a flattened linear list rather than taking advantage of the merge structure of a branch. This also sounds like something that should be relatively easy to make smarter.