Is there a mod that will display messages (e.g. command lists) that players have set in the chat box when they log in?
I'd like it to only be displayed to logged-in players, not as a login notification.

Welcome Messages or Welcomer and try looking through the plugins available

not as a login notification?

Using either of those mentioned would display the information when someone joins, some can be set so that they only appear when the user connects for the first time 

I don't want to display messages like "XXXX has joined from USA". I want to display a specific message only to that player when they log in.

obviously you have not read what those plugins do, you are not being told to use ConnectMessages or similar plugin,

I'll try a little harder

My WelcomeMessages lang file copy
{
"Welcome": "[#00ffffff]Welcome to *********** CAN YOU Survive {0} ??[/#]
\n[#ffff00ff] For KIT MENU type / kit do NOT REDEEM KITS with a full inventory[/#]
\n[#00ff00ff] WARNING SERVER DECAY is ON : TWIGS , WOOD AND STONE DECAY [/#]
\n[#00ff00ff] WARNING You WILL be KICKED for ANY RACIST names or ANY advertising [/#]
\n[#ffff00ff] THIS IS NOT A CREATIVE SERVER[/#]
\n[#ffff00ff] WATCH OUT for the HUNTERS guarding the animals[/#]
\n[#ffff00ff] Rules and hints will scroll Top Right of screen[/#]
\n[#ffff00ff] WATCH OUT FOR NPC Patrols in Monument areas and Map[/#]
\n[#00ff00ff] The MORE you Gather / Craft = Gives you higher / faster rates[/#]"
}

And thats it for me due to lack of interest