If you are suggesting a change in something related to the forum, the more fitting board would be Meta rather than Beginners & Help.

The Activity is the lesser of the two parameters implicate in ranking-up (Merit,Activity), and is by far the simplest to achieve. You’ve barely been on the forum enough time to appreciate that Activity actually grows pretty slow, and is capped to 14 points per fortnight in broad terms. It will take many more posts for the common forum member to obtain Merits than to obtain Activity, so I would not really consider Activity as a contributor to spam (by that rule of thumb, Merits would be a far greater contributer).

On the other hand, logged-in time on the forum is easy to rig. I could leave a process performing queries every minute 24/7 pretty easily, and multiple while at it. It does not equate learning the ropes of the forum, and far less being able to post decent enough content.