Some members, though definitely not most, frequent the chat area, where you can ping them directly by @reemrevnivek (or @whatever). If their name doesn't "pop up" when partially typed, then the ping probably won't work unless you point to their chat history. One way to do that is to go to the 'info' page for the chat room and click 'Frequently In Room', click one, click the 'recent' tab, then click the permalink symbol on the left-hand-side of one of the chat bubbles (it'll pop into view upon mouseover). The address will be something like:
Copy the number on the end,
2889163, then head to the chat room. Type
:2889163 and that user will be pinged (and it'll look like you're replying to the referred chat bubble, but oh well).
That was complicated. A better option is to spread general cheer with ebeers.
I often thank users for thoughtful answers in comments directly on their answer.