EssentialsX version (run /essentials):
Server software (run /version):
Screenshot with all informations you need.

Server (logs/latest.log):
Latest Log

EssentialsX config (plugins/Essentials/config.yml):
Ess-Config I'm using.

Details:
You can see that I'm using the latest build of EssentialsX and I got this annoying [L] in front of my name. First I was thinking it is from another plugin, but it wasn't. It's definetly from EssentialsChat.
I use no mods in my client and, as you can see in the screenshot, there are no other plugins installed.

Regards

You have LocalChat enabled; change the number to zero to disable it.

Oh my! This is that! Man! Could'nt find any description of that! Now its clear!
Thank you!