So according to this ruling, the minimum to the maximum hand size is only applied at the time the Pillowbook enters play, and ceases to apply when another similar continuous effect without the minimum clause begins to apply... This is a non-unique card, so I'm curious on the situations this may cause.
Let's say I'm playing Spider and have a Dragon opponent. I buy one personality and attach Pillowbook, and then I buy Taishuu XP. His maximum hand size would be 8-1-1 = 6 Correct? Opponent then flips Togashi's Guidance XP. His maximum hand size would go back to 8 (8-1-1+2). So I attach a second Pillowbook, and move him back to maximum hand size 7. Then Dragon opponent discards Togashi's Guidance XP to fetch a Ring. Would he still be at 7 because of the minimum imposed by the second Pillowbook (making discarding the Celestial a good call) or would he move to 5 because of the end of Togashi's Guidance XP's trait (8-1-1-1)? Later Taishuu XP dies and reacts with Feign Death, entering play again. Will my opponent's maximum hand size be reduced to 5 (8-1-1-1)? Assuming his maximum hand size is now 5, If I attach the third Pillowbook would he move back to 7 (making it a not so good call)?
On the other side, my maximum hand size is now 10 because of 2x Pillowbooks, and my opponent's is 5 (Taishuu being the last to enter play in this case). My opponent then plays his own 3xPillobooks. My hand size reduces to 7 (8+1+1-1-1-1). Does his hand size move up to 8 or to 10, since the last effect that modified his hand size (his own Pillowbooks) didn't have a minimum? Or is it only the opponent's cards what matter? If my 2xPillowbooks are then destroyed (eg Gold and Steel), would I still be at 7 (because of the minimum imposed by his Pillowbooks) or 5 (because the minimum wouldn't be rechecked continuously)?
After considerable discussion, the rules for calculating effective stats have been changed to accomodate bonuses "to a maximum" and penalties "to a minimum": To get a stat's current value at any given time, do steps A through D, below: A: Apply all current bonuses and penalties that are not restricted by “to a minimum” or “to a maximum”. B: Apply all current bonuses and penalties that are restricted by “to a minimum” or “to a maximum”; applying maximum-restricted bonuses first in ascending order of the maximum's numerical value, then minimum-restricted penalties in descending order of the minimum's value. The restriction means that if that particular bonus or penalty would take the stat below that minimum or above that maximum, its amount is reduced until it is only enough to reach that minimum or maximum. [ADDED 13 Jun 2012] C: If the total is below 0, treat it as 0, unless the stat is Family Honor, Honor Requirement, or a modifier with a + or – sign such as an Item’s Force and Chi stats. D: If the total is less than the highest minimum value in effect for that stat, or more than the lowest maximum value in effect, it becomes that minimum or maximum. See above under “Maximums and minimums” for what happens when a stat is less than a minimum and greater than a maximum at the same time.
Thus, a penalty "to a minimum of X" cannot help to reduce that stat below X, but if other penalties - ignoring the penalty "to a minimum" but including relevant bonuses - are sufficient to reduce the stat below X, then they will do so.
This does change how some cards work, for example the Obsidian Dragon, but hopefully is a simpler and more intuitive rule to apply.
So, if I have Taishuu and a Pillowbook in play (brought into play in any order), your maximum handsize is 8 - 1 (from Taishuu) = 7, and the -1 from Pillowbook does not apply. If I have a Taishuu and a Pillowbook and you also have a Pillowbook, your maximum handsize is 8 - 1 (Taishuu) + 1 (your Pillowbook) = 8, -1 (my Pillowbook) = 7.