Ok so my unrelated account was able to close this issue, and I seem to be able to close others' issues even though I just signed up for a random account. I don't think I should be able to.

Sorry, I know this is the wrong component, but I don't know which of the 2k components this applies to as it's really a meta-issue.

I moved this to the INFRA project and "jira" component because that seems to be where other issues for the https://issues.jenkins-ci.org/ instance are filed.

However, I expect that the Jira administrators won't want to start restricting who can close issues, because that would require them to start maintaining access control lists and would make it harder for people to join in and help. If someone mistakenly closes an issue in good faith, it is easy enough to reopen. Spammers have financial incentive to post spam comments but I think not to close issues.

See also Project Governance Document: "We strive for lower barrier of entry to the project."

Kalle Niemitalo is correct that this is intentional. We allow a low barrier of entry so that people can assist in the project in many different ways as their time and capacity allows.