You don't need to have a business to have a signature. As mentioned above, you can upgrade to a 'Community' member, help support the great work that goes into this amazing resource and you can have a signature as well as other benefits.
You don't need to pay a membership to support the site. You are here contributing that is also support. This forum would not be worth anything without people contributing the one thing that is worth more than money - their time.
While this is true - and contributions (including just asking questions) definitely qualifies as supporting the site in its own way ... it doesn't actually help pay the bills - not directly. Premium membership is only $9.90 per month, or $99 per year and helps keep this site running.
That's just a quirk of the way I had it set up - the Closed "prefix" on the thread meant that the original issue no longer needed my attention (from a helpdesk perspective). I don't tend to use that structure anymore - but never got around to removing the closed prefixes from the threads. Not the same as actually closing a thread so that no more replies can be made - that's a different process.
