This sounds like a recipe for write-only comments. The point of a good comment is to guide later development - to say "here's something you should know before

This sounds like a recipe for write-only comments. The point of a good comment is to guide later development - to say "here's something you should know before editing this code". If you put information like that in commit logs, then that implies that anybody who updates any part of that codebase must first read every log for every commit near what they're editing. If they don't (and they presumably won't), they'll never see that "here's why we're not doing X" comment before they change the code to do X. Meanwhile, it's true that comments can drift away from truth over time, but putting them in commit logs doesn't change that in any way. An inline comment that's stale can be updated (and doing so is part of the job!). But a commit log comment that's no longer accurate will stay there forever, waiting to mislead anyone who finds it. The promise that it was accurate when originally written is of no practical use later on.