I noticed that my original tab characters in code snippet in Edit text box will be converted to white spaces when they are viewed on the rendered HTML. Ones who want to try my code usually copy the code from the rendered HTML. But for some special case where the tabs are valuable things, the output they will get will be totally different from mine. Code indentation gets lost in Beamer is the non-trivial example where changing tabs to spaces will make different result.
We can avoid this issue if they copy my code by entering the edit mode first, removing the code mark down, copying it and pasting it to their editor. But non-registered users cannot enter the edit mode.