The rules would be:
1) each Hatracker can only add one sentence/post; after you add one, you have to wait until 3 different hatrackers have contributed before you add another one.

2) the one line you write has to connect with what's happening in the previous lines and the story overall in a logical way.

3) If the last line of the previous post forms a natural paragraph end, start a new paragraph, but write only one line of it and make it a natural continuation of the story.

4) if someone posted a line before you could - tough. Modify your post and either add the next line after him/her (if not violating rule #1) or make your post blank and wait until others have posted so you can add a line again.

Repeat until we have come to a natural conclusion to the story.

The idea is to focus on the actual written words others have posted and get a feel for the story and practice developing the natural next line to all the prose that came before - a sort of practice antidote to writer's block.

And We can publish it as by "Mr. Hat Rack"!

Of course we would, Dark, read the bylaws.

Section 1.8.5 of the SFWA Code: Membership solicitations:
"He who so contributeth the merest comma to any published work shall be ableth to solicit membership of the SFWA at a cost proportional to the amount of characters contributed as to the total sum in the work, and be likewise grantedeth privileges exactly proportional to the cost as to cost of standard membership."

If I remember, or manage to find one or more, I'll post a link here.

However, I still read many first 13s mostly cuz I want learn for myself which openings really catch me - and analyzse why.

But for ones that don't work, I rarely post comments - only if I feel there is something valuable I can contribute - where i have a specific idea what went wrong and a suggestion of how to fix it. If the author implements it - I can see if the suggestion worked.

Also a lot of the opening 13, in my view (just being honest), are either terrible or don't make me want to read further - it's not that their opening might be bad, even famous published work have openings that are, to me, very dreadful - and I usually don't have much in the form of a supportive critique other than "it doesn't work for me- rework it." So I just keep silent and let more astute readers comment, rather than be another claw at the new writer's fairly thin tender skin.