TileEntitySign's

public void a(EntityHuman entityhuman, boolean flag, List<FilteredText> list) {
if (!this.w() && entityhuman.ct().equals(this.v()) && this.o != null) {
...

entityhuman.ct().equals(this.v()) should be entityhuman.cs().equals(this.v()) ??

ct() returns String (from UUID.toString(), whereas cs() returns UUID.

TileEntitySign's v() returns UUID.