It looks like Turbine is going to allow LOTRO to be moddable through use of the LUA scripting language. Massively post here about it.
I don’t have much experience about mods, except that FFXI used them heavily for the PC crowd. Windower allowed you to alt-tab the game, which was harmless-but then we got extended macros which were impossible for PS2 users, autoloot and autosort, distance plugins, etc.
I don’t think modding is good because it alters the game to a point where devs often need to play catch-up. Mods can make the game far easier, so that means Turbine is going to have to factor them into new content. That will also make it much harder for non-modded players.
It’s also interesting to me that they are doing this. My guess is to try and catch more WoW or ex-WoW players used to a heavily modded interface.