In fact, it could be a very good thing, especially if the alternative is, eg, dropdowns for type and scope, and a separate popup for editing or adding new ones, and so on.
Having the data model loosely encoded as text, and understood only by convention among humans, who can then improvise changes to that model in exceptional cases, relying on other humans to make sense of those changes even though they are "outside" the agreed-upon model, is sometimes exactly what you want.
Also, as UI for input, text is often the fastest and most efficient -- again, just what you want. Of course, you could always do string validation on the text input to enforce your model, so this can be considered an orthogonal point.
And these considerations don't even touch upon the increased complexity and maintenance costs that your tool itself (in this case, git) will incur if it takes on the burden of maintaining the data model explicitly.
The UX exists for the reader, the data model for the programmer. Sometimes, text is the best UX. For example, I love Markdown, a classic example of a data model serialized as text. I do not want a “rich editor” that speaks the data model directly.
There is a big deal of subjectivity (e.g. what is a bug, and what is a feature) but (as with any comments in the code) it is nice to see at least what was intended (e.g. someone wanted to position a misaligned button, or added it, or improved its visuals or optimized its click from O(n!) to O(1), ...).
Well, for starters I wouldn't have a commit message stating that I just added a bug, though I might have one stating that I added a feature. :P
I'm curious:
In any tool for any revision control system ever: in a list of commits, are the commit messages augmented with something useful beyond the basics? ("Basics" being e.g. the first 'n' characters of the human-provided commit message, a revision identifier, a timestamp, and a username.)
Jira and other ticketing systems can often read repos and look for ticket ids. In my commits at work I just mention PRJCTNAME-142 and that'll link to a ticket and aggregate in jira all the commits/pull requeusts/branches... tagged with that