I think it would be pretty useful to enhance the Markdown editor for writing issues or PR descriptions, or any other messages on tangled.org
The feature I personally use the most on similar platforms is the "Preview" to see if my syntax actually is correct before submitting.
To get the real Markdown editor feature, we could also think about adding the typical buttons for "Bold", "Italic", "Strikethrough", etc. Inserting empty tables with arbitrary size would be advanced, but I would assume that we could compare some libraries which already ship performant Markdown editors (research needed).