The only issue with using too many spaces is that the file size of the 2DA increases noticeably, if you use LibreOffice Calc, you will notice the difference almost immediately as that cuts down the spaces automatically with the “merge delimiter” options, I had 2DAs cut down by 70% in size thanks to that.
Especially custom feat.2da and spells.2da used by various servers. (NWN2 default 2das come optimized by default it seems)
Of course this will make the 2da look like a “mess” if you open it with notepad, but that is something I wouldn’t recommend doing anyway.
And while I’m not 100% sure about this, I do think that cutting down the size of a 2DA file makes the Get2daString function a little more efficient and/or reduces the memory usage when you cache that 2DA with the Get2DANumRows (or columns) one.