I've installed MrCrayfishFurnitureMod in a server along with some other mods, and the message written when placing the doormat isn't showing up.

When I tried placing mine in a server it crashed my game and now it's a missing chunk. RIP house.

If it crashed, make sure you update to the latest version.

Can't seem to reproduce. Make sure you're using the latest versions of the mod. If you're using 1.12.2 I won't be fixing any issues like that since it's discontinued.