Thanks for the information. Just to clarify information will flow from any HTPC back to the server(noted that MC18 is not running in server mode on my media server).
Not sure we got you right : to which library are your htpc connected ? if you run mc on the server (machine) and also on each htpc locally changes you do will remain local. To have all changes reflected the MC on your server needs to be the "main" database/library. + you enable the MC server under tools>option>network.
Then on each of your HTPC you open the library manager and select add a new library. You will then select the above mentioned library (running locally on your server). In doing so all your HTPC will have all latest changes you do from any of your htpc.
Does this clarify or help you see how MC is run in a server/client environment ? Am not sure this is new to you but your statement (noted that MC18 is not running in server mode) let me think that you actually only share the source files on the server and not the MC library holding the source files on the server