That one in particular strikes me as kinda awkward - .co vs .com is prime real estate for trouble. But I’m not looking to use a .co, just to understand if I can/should push on with a good (+industry applicable) eight letter brand name where the .com is effectively dormant but I don’t own it, or whether I should come up with another name where I can get the .com.
It does not matter, but it's usually better to own the .com. I think the . community extension is really good for forums, and I also use a . community domain for my site.
I think the primary difference between .co and .com comes down to awareness and user behavior. Most people are naturally accustomed to typing .com because it’s the most widely recognized and established domain extension. While .co isn’t as well-known, which leads to less intuitive use by the general public
I don't think a .com matters as much as it once did, I think it's more creative when websites use domain names that finish the name of their site. For example, I'm using Thee.Zone for my forum Thee Zone. I also own the sonichack.ing domain name which I'm using for a Sonic hacking related website.