What causes an old question to (seemingly) randomly be brought to the front/top of the Stack?

Question

Relatively regularly, I'll come to the page and see an interesting question or one that otherwise draws my attention in some way. At some point while preparing a comment or answer I end up noticing that the question is a year or two old and there has been no recent activity (answer, comment, edit, etc.) to it. Yet, nonetheless, it is at the forefront of the page. This question is one example: Can a medical professional be liable for not completing a procedure as claimed?. It's from 2017 but today (4/4/20) it's listed as the first/top question.

My question is why does that happen and/or how does that get determined? Any insight on this is appreciated. Thanks.

Answer 1

There is, in fact, a procedure for bumping questions. That's what happened to the question you mentioned. In brief:

The Community user will bump non-negatively scored, open questions every hour that have at least one answer scoring 0 and none scoring more than that.

Questions are picked randomly from the top-viewed questions with last activity more than 30 days ago.

Once a question is bumped, it will be ineligible for bumping for the next 120 days, unless it receives new activity after the last bump. (Bumping a question counts as new activity, so at a given time, questions bumped within the last 30 days are guaranteed not to be bumped.)

The maximum number of unanswered questions bumped per hour depends on the site: 4 per hour on Stack Overflow, 2 per hour on Super User and Server Fault, and 1 per hour on Meta Stack Exchange and all other sites.

Some sites have limits on how many auto-bumped questions can appear on the homepage. Once the limit is reached, no more questions will be bumped until one or more bumped questions disappears off the homepage.