"Dear" for expensive ("I can't buy it right now, it's too dear.") is used very often in Australian and British English. Perhaps it's not common in American English, but it isn't wrong.  

Your article is very comprehensive.  I would only add one common difficulty: what / that.

It seems that some students have difficulty knowing how to translate что in noun clauses:

Anything what he says is untrue.

Anything that he says is untrue.

Maybe it's a regional difference. Here "to feel yourself" only means "to masturbate" and if you used it to describe emotions people would think you're not a native speaker.

The article is really great! That's a pity beginners can't understand it because it's written in English :) As Russian native speaker I can explain why we keep repeating "feel myself". Teachers at school are usually too shy to explain the true meaning of this phrase, so they just tell their students that they shouldn't say it. But people easily forget it because prohibition seems unmotivated. And the rest is direct translation from Russian and it can be cured with reading and listening in English.

Nice article!  I liked reading it.  I hadn't taught many Russian students 'til I started advertising on italki and all of your comments are spot-on, IMHO.

What Thaddeus mentioned about 'what / that' and what you said about avoiding / not constructing noun phrases correctly -- that is the biggest thing that prevents speakers from formulating complex subject / objects and thus, being more precise / clear.

SIMPLE: I did the report with my colleague.

PROFESSIONAL / FLUENT: I did the report that was due on Friday with my colleague who is here visiting from Head Office. 

I am forever prompting for this missing information...what report?  which colleague?

And yes, I do realise these are the problems of intermediate > advanced students and not applicable or appropriate for beginners / low intermediate.

I would love to hear about modality in Russian.  That is another area where the upper intermediate students get lost and there has been so much attention to SIMPLIFYING things.  Students don't realise / won't accept that 1) there are multiple ways to put conditional sentences together and 2) spoken discourse is agile and rarely emerges as perfectly constructed in sentences -- that, for example, often either the 'if' clause or the main clause is omitted in speech (but the meaning is definitely hypoethical or unreal, etc)