How to sign a message with my node?

In LND, you can sign like this:

lncli signmessage "this is the message to sign"

In C-Lightning:

signmessage "this is the message to sign"

Eclair:

eclair-cli signmessage --msg=$(echo -n 'this is the message to sign' | base64)

Please can you advise re: the below? 

In RTL:

1) I paste the text you've shown above (lncli signmessage "this is the message to sign") into the 'Message to sign' field
2) Click 'Sign'
3) This generates a string of letters & numbers in the 'Generated Signature' field
4) I 'Copy Signature', click on 'Verify'
5) In 'Message to verify', I paste in the same message as in 1)
6) In 'Signature provided', I paste the same string of letters/numbers as in 3)
7) Click 'Verify'.  This now shows my public key with a button to 'Copy pubkey'
8) I put the 'Generated Signature' into your 'LN Node Verification' https://lightningnetwork.plus/node_verify , click 'Verify Ownership' but keep getting a 'Sorry, the node you signed with doesn't match the node id in your profile'....even though it does match!
9) What to do?!!

Thanks! :-)  

Both Ride the Lightning and ThunderHub make it very easy to sign and verify messages.

Here's where to find the tools: