Thread starters and thread joiners-in in particular.
It keeps the forum lively, and when anyone logs in, its always better to have something new to view, and join in with if you so desire. Also participation encourages participation.
On the other side there is nothing more discouraging to participation than lack of comment or response.
I think we all miss CitroJim's activity on this forum and all wish him well. His fine example of joining in is second to none.
Whenever I look at "who is online" its generally very sparsely populated these days which makes active participation even more vital, although like this screenshot the "bots" and "crawlers" always ever presents!

- screenshot
REgards Neil