[esens]

Could be in a service on a server, which in this case a RegEx DOS could lock the server for all users.

[JonathonW]

Or if a JS frontend takes in input that comes from other users-- something like forum post titles or content.

That's "just" a browser freeze for end users, but still a potential DOS vulnerability if it's in the application's critical path.

[nkozyra]

Right, but that's why I wrote "context," and seems to be the primary complaint in this article.