Филашкин

Work! Thank you!)

So?

/blockdata ~ ~1 ~ {Text1:"{text:1,clickEvent:{action:run_command,value:\"say Hello World!\"},bold:true}",Text2:"{text:2,bold:true}",Text3:"{text:3,bold:true}",Text4:"{text:4,bold:true}"}

Still not working

/setblock ~ ~1 ~ minecraft:wall_sign 4 replace {Text2:"{clickEvent:{action:\"run_command\",value:\"say Hello world!\"},text:\"TEST\"}"}

This command works in 1.8.8 if click to sign.

I find it hard to look for something in an incomprehensible language I. I just reported an error. What to do next - see for yourself.