Now the part that speaks about how to deter investors from buying shortly before the dividend payout and selling after without this affecting the price of the tokens is what I am trying to grasp.

Let's assume that the dividend sharedrop for an example UIA was always scheduled for the 24th of each month.

If 'coin-age' (how long the UIA has been in your BTS wallet) was not taken into account, I could buy the token on the 23rd, receive the dividend on the 24th then sell it on the 25th. We would see large buy pressure immediately prior then a large sell-off afterwards, which potentially isn't healthy for the token.

We have seen this kind of behaviour in the past with sharedrops against Protoshares and Bitshares, heck Peerplays kept the sharedrop date against BTS secret & only issued a range of dates in which the sharedrop may take place as to avoid disrupting the BTS marketcap.

Grasped the optional need for coin-age now? If not, ask away :)