I think that there is a lot of variety among posters.
The ones that are currently a seriously training high school, college, or recent post-collegiate, and the ones that are older and did this in their youth do, I suspect form a very large group. Probably nowhere else on the internet is this group so well represented. This is the group that regularly displays their track and field knowledge.
This group can/have/or will all break 2:00 in the 800, if they were middle distance. I am not qualified to guess where the sprinters fit in, but this group is more middle and long distance than anything else.
But it is also clear that this is not the only gourd of people on the site. There are hobby joggers here, ranging up to the super serious hobby jogger, many of whom have no youthful background in track and field.
And then there are the clear cut crazies that have found the site somehow, many of whom I think have little to no connection to the sport