Although this is something I missed since I just know that deleting posts will also decrease the activity of that member I thought activity was something permanent once the player reach it.
The forum allows one user has 14 activity points in maximum for each 14 days. The interesting point (that you missed) is that one has to post a single post to get the potential 14 activity points for each 14-days period. Later on, 3 months, 6 months later, he can be more actively post more than 14 posts for each 14-days period and all redundant posts (15th to 20th, ie.) will be counted for the period that was marked with 1 post for that period.
Let's imagine there are 2 period in this July:
- 1st - 2nd weeks of July: I make only 1 post
- 3rd - 4th weeks of July: I make 27 posts
I will get exactly 28 activity points for all 28 days in July (to keep it simple as that, let's assume July has only 28 days).
Next, if you delete 26 posts during 3rd to 4th weeks of July, you will still have one post to mark that period so that you can post more and get a maximum 14 activity points for that period later. If you delete all 28 posts, and no posts left to mark those 4 weeks, it is impossible to make extra posts and get activity points later.
About
BobLawblaw who has been demoted to Member. Now, he has 62 posts in total.
Assume that he has those 62 posts to mark for 62 periods (14 days for each, each post mark each of 62 periods), he will be able to get a maximum activity points at 868 (62*14 = 868) if he make enough extra posts later.