I tried to insert an Emoji symbol in TextMate and Sublime Text 2. Both couldn't do it. On the Mac, Emojis seem to use a special font: "AppleColorEmoji". On iOS, the Emoji keyboard just inserts special Unicode characters instead. It looks like those two methods are not really compatible, but I may be wrong.

What is S-Drive? Do you have a link?

What kind of server are you running? It would be nice if you could give me enough information so that I can try to reproduce it on my machine.

It could also be an encoding problem. I'll try it tomorrow.

Maybe you entered symbols that don't exist in the font files on the iPad.

I did enter them using the Emoji keyboard on the iPad. You can add this keyboard in Settings on your device.

Yes, implementing a "Show invisibles" feature instead of just "Show tabs" would definitely be very useful!

At the moment, Textastic can show tab characters as gray triangles.

I have just tried it and it works for me with all fonts. See the attached screenshot.