Surely the point of a forum is that questions and answers are public and other people can benefit from/criticise any advice given.
I suspect where non-forum users contacting users is concerned I’d imagine that its people who are researching a topic and come across a conversation here. I’ve been in situations where I’ve been researching stuff online and the best lead thats come up has been an online conversation on a forum somewhere. However STWs forums are uncommonly busy with the bulk of the chat coming from a relatively small ‘family’ of frequent posters
When I’ve researched topics and found a conversation on, say, a pigeon-fanciers forum its a comparative ghost town. The post rate is low, the frequency that users revisit the forum is low, so if you create a login and join the conversation….. nothing happens.
So if someone stumbles onto a topic on STW they won’t necessarily realise that to speak to DD you’d just have to join in on the tread and your question would find him – especially if a thread is month or years old