Idk, I feel like most people that post in the "coping with social anxiety" section are looking for advice. As far as the "frustration" section its hard to tell but I do feel like most want advice or they wouldn't be posting. To me if you want to strictly vent with no input then why not just blog it.
Yeah I guess that is true. It's hard to tell though, what the person wants out of the post sometimes. Do they want support in the form of possible solutions, advice, in the form of "it'll be okay", or in the form of "I just wanna talk about". The latter two could be meant for frustration where the first two could be meant for seeking advice.
EDIT the forum description says : Ask questions, give advice and share your knowledge of how to cope with SA. If you are over 30, you can also post in our 30+ Members forum if you prefer. So yeah I didn't see that thank you Kevin001!