Bro TinyPrick: Good post.
Initially I also felt the same kind of irritations and Reviewustrations when I desperately open the page seeing a recent post in the thread (i am a senior to you bey a couple of months as per registration, but have been on this site as a guest for a long time). But after sometime reconciled to beleive that this is perhaps the SOP.
There could be a few reasons why this habit is there which is worth analysing:
1. The MBox of the TS may be clogged virtually making him suffer the deluge - which is now seen in the thread. For having had the generosity to share he would feel punished to keep deleting 100s of requests to keep his box clean.
2. If all in a thread TS can rapidly scan through all the requests; obviously he would normally not share with all so he may have criteria like seniority, active posts, points, power before selecting to respond to a request. This save TS some effort.
3. I wonder if the site owners have some interest here too (do not wish to sound critical but just wondering). Sites like these (meaning any site or forum), needs some activity for increasing their popularity. So more the posts better is the cost-equation for the site owner (I may be wrong in this).
And there could be a few more possible reasons, but to keep my post sounding boring, I stop here.
Thanks bro for reciprocating my initial feelings; after sometime you get used to it like the way my tiny prick nowadays remains tiny even at the site of a sexy girl. Fucking many makes it routine. So applies to good world as well as the bad.