Well, Kate colors according to a lot of programming language schemes and shows additionally near the right margin a picture(!) of the entire text with all indentations and a window-like marker of the position where you are just working...

So does Emacs.

There is an Emacs plug-in for that.

Use it since a couple of years, happy with it, but will be more happy if some more (even if prorietary...) languages will be configured for enhance editing (ex.: PlSql, vb, ...)

My buddy is a fan of Vi, whereas I tend to do most of my editing in mc. I have been using mc and, without meaning to date myself, its predecessor Norton Commander -- yes from the days of DOS 3.3 some 30+ years ago -- which is a small but powerful utility that allows me to do everything, including text editing.Originally I got Sublime more for my buddy when he is working on my machine, since he feels more comfortable using Vi, than for myself, and for the rare occasions where I needed something more powerful than mc. While exploring Sublime together he discovered that does some crazy stuff that Vi does not do (I think he said something programming languages or some such thing, but don't quote me on that). For me most of my editing is light duty work that if it involves coding or some such thing is usually confined to a modification of a line or two, the rest is simply text editing and mc is more than up to the job for that -- one does not need an elephant gun to kill a mosquito, but its nice to have the elephant gun if there is a likelihood you may need to shoot an elephant. I have discovered there are times when editing stuff is either foolish or not possible in mc, I can in Sublime, and now find myself using it -- no matter how rarely -- more and more often.

Most of the time it's Pluma. But when I need a fully-featured one, it's still Emacs

I voted for vim because it is my go to editor.

From people who are Vi and Vim people Sublime is "sort of like Vim but on Steroids" (a direct quote I have no way to know). I myself am a mc type of person but still voted for Sublime because its the BIG gun you haul out when you need to do SERIOUS editing -- thankfully for me I seldom need to do a whole lot of that type of editing. I'd encourage you to download a copy and play with it. The transition from Vim to Sublime probably will take you almost no time at all I'd guess.

On the command-line, vi*, pico/nano, and theoretically MCE or (if still works) SETEdit, and I used to like KATE, but please add Notepadqq. It's like Notepad++ (free Windows program inspired by Notepad and the original ultra-useful/-powerful commercial tabbed text-editor/IDE, UltraEdit) but for GNU/Linux, and is like KATE for X Window System & KDE, but not KATE's all-insufficient/-buggy/-broken tab bars (and Notepadqq is also like gedit for GNOME but automatically does some/many advanced things gedit requires manual setup.) Like KATE & gedit, Notepadqq doesn't force you to use it like an IDE so much as some others on the list... every such thing can be configured so it can be just a text editor, or mainly an IDE, or a very nice balance of both.

I went for Xed 'cos it comes with Cinnamon DE. But I also use BlueFish to edit text files.

But I'm not fussy at all and I have experimented with vi and vim.

gedit was the first one I ever used when I converted from $$ to Linux with Ubuntu 8.04 back in 2008.
I have enjoyed the elegant simplicity of leafpad when using LXDE on Debian.
Scite is pretty cool, I discovered it as a Linux alternative to the $$ version of Notepad++ a long time ago. Scite has a few add-ons that I found useful. I haven't used it in a long while, maybe now is the time to give it a spin.

Kwrite, Kate and nano, in that order.
So my choice Kwrite.

Vim all the way!

VIM, as its easiest for me to use when I login remotely to my work PC and still need something powerful.

vim

gedit - for gui or command line use.

Atom, the text colouring is cool and the plugin system is awesome