Hi
Your link is to a whole blog- no chance of finding the specific schematic.
Are you referring to the pull-up reistors and diodes on the sync lines?
They are simply there to clamp the DC levels of the sync pulses.
The link is to the post which contains pictures of the board.
The H and V lines are, indeed, protected by a diode.
One EMI filter is in series, just before the vga connector, of each of the h and v lines.
I tried you link again. Takes me to a page full of stuff that I'm not going to bother sieving.
I also got a page of rather confused discussion of prehistoric game console video outputs...
The sync outputs are likely driven by some sort of digital logic output which will have a rather fast edge rate in comparison to the output of whatever video DAC the thing uses, I think I would probably throw some filtering on there if I was designing it.
Probably just some sort of small ferrite bead and a 100pF cap, should be fine.
There's no DAC in the device itself, it goes straight into the monitor.