This isn't text, you're using ASCII symbols as pixels in a grid to represent a raster image. This is literally just a raster image on an unconventional canvas.

If you treat a uniwidth character grid of characters as pixels, you have not converted an image into text, you have encoded text into an image. It's no different than using extended characters and font colors in a fixed width terminal window to make terminal art.

The fact that you use UTF-8 to encode something does not mean it will magically work in a screen reader, or that it will retain any of the advantages of pure text. I can encode any image or video file in a UTF-8 format and send it to you. Down this path lies calling everything text.

But if your "text" stops being readable if I disable monospace, or it stops working if I change the font, or it stops working if I change line wrapping, or it stops being communicable as soon as I try to read it out loud -- then it's not pure text. Using a UTF-8 character as a pixel does not change the fact that you're drawing an image out of pixels.

That does not even remotely represent the Twitter logo, though. Shape and color are completely lost information, which are essentially the key properties that make the Twitter logo the Twitter logo.