I have a question about parts for a circuit (specifically solenoids), but I'm unsure where to ask it as I've heard that it is taboo to ask for suggestions for parts on any '.SE forum. Would the EE.SE chat be an acceptable place to ask?
As Nick mentioned in a comment chat is a good place to ask those sorts of questions and I've asked a few component sourcing / recommendations questions in the past with good results. Although the name "chat" implies real-time (which it is if someone is around) often because of time zone differences and peoples availability it might take a while to get a response.
From that point of view just remember to start your message with something like "@PeterJ" when replying to someone that has replied to you and they'll get a notification in their inbox when visiting any Stack Exchange site. The only thing to avoid (other than if generally just saying hello) is doing that to random people who happen to have been in chat recently unless you happen to be familiar enough with the person to know they might be able / interested in that particular topic.