I am still a bit unclear by the phrase, "Avoid address reuse." in the high level design doc.  It could me strictly mean do not reuse address, or it could mean do not associate addresses (as in co-joining two addresses into a third address), or do not mix the dirty laundry with the clean laundry.  I found the figure in Wikipedia's coinjoining page more illuminated than the figures in the high level doc and in Gregory Maxwell's.  It appears as though from Wikipedia's figure, that the privacy is a function of the depth level.

Let L represent the depth level and P the privacy, then P=P(L) where P strictly increase with L.   That is to say that change addresses remain tainted.

Also, since the transaction fees are so high now, it seems reasonable to consider consolidating coins into one address (for both makers and takers which would require takers to run a full node), so as to lower the kb of transactions.  I am still a little fuzzy about the the number of UTXO per users.

Is this proposition correct?
Let N=the number of user, then N-1=the number of makers. Let O=the number of UTXO going into the coinjoin. Let M=the average number of transaction inputs per user

N*M<=O

Hence by running a full node the users increase reliability and lower the need for more than one input and lowering the lower bound of each of the following transaction inputs, transaction data size,  the transaction fee.