It seems that with the fix for
#6315, path-absolute links that used to resolve now are translated into broken links. For example, I used to link to issues in other projects like so: See Setuptools 230. If that had been rendered by Bitbucket months ago, it would have resolved to the issue in the bitbucket project. Today, it resolves as a file in the source tree for project in which the issue was filed.
I admit that the server-relative, path-absolute links may have been an incidental function that worked only because it relied on the browser's link resolution convention (where path-absolute links are resolved server-relative). I suspect few users ever knew this function existed, and even fewer used it.
However, the effect is that many of the comments I've made are now broken.
I am mostly filing this report to create a record of the issue. It would be helpful if Bitbucket could run a report of posts (issue descriptions, wikis, and comments), preferably indexed by the user who made them, that make server-relative path references before the change was made. Then, I could go through the report and correct those comments. Even better would be to proactively re-write them with absolute HREFs.
I acknowledge that might be a lot of work with a small payoff, so if you choose to close this as won't fix, I understand, and I'll correct the broken links as I encounter them.