The person you are replying to here (triska) is the original bug opener Markus Triska. A skim read of the thread, there's a long back-and-forth of Prolog parsing and formatting and interaction with Emacs movements, with many bugs raised in it. (It's more of a review-and-polish something than a single bug), and near the end Stefan Monnier says:
> "OK, let's turn things around, indeed: we revert to Stefan Bruda's indentation code, you're handed responsibility over that code, and I get to send you the bug reports about all the regressions this will introduce."
It's not clear if that's meant genuinely or frustratedly and sarcastically, but it's taken genuinely and Markus Triska replies: "This would be a good improvement in most respects I consider important, thank you! I will treat all issues you and others send to me with great care and attention, and work on correcting all regressions and issues I can. I have a lot of experience editing Prolog code with Emacs and can spot regressions quickly."
Followed by Stefan Monnier apparently not doing that, and fixing two (of many) issues raised and discussed. (Perhaps he considered it handed over and that the next action would be patches from Markus Triska?) Then 5 years later Lars (who wasn't involved in it?) closing the whole thing without reading it in detail, taking that as "whole thing fixed".
It's not too far from Zawinski's "Cascade of Attention Deficit Teenagers" model[1] of open source bug reporting - they go unread for years, then get closed with "if it's still a problem, make a new bug".
[1] https://web.archive.org/web/20210311012401/https://www.jwz.o...