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There is a plugin which makes the entry of greek characters with combining diacritics easier, called BetaCode. Looking at its source code, it does the following:

# Unicode normalization, make chars precomposed whenever possible.

 str = unicodedata.normalize('NFKC', str)

I don't know a lot about unicode, but it seems that if pasted text containing unicode were normalised in this fashion then combining diacritics would render correctly, at least in the particular case of greek letters.

You can show whitespace characters all the time by setting
"draw_white_space": "all"In your user file preferences. This is a little distracting though, and certainly a lot noisier than showing just indentation lines like in the link originally posted.
In the case of the "target" folder though, this is not necessarily something I would like to set as a global preference, but something attached to the particular project I'm working on. Anyway, adding it to the global preferences isn't going to cause many problems for me personally so I'll go with this for now.