@WW I am not blackening the 123 approach; it is a much-needed crutch at intermediate and i use it religiously. Indeed one cannot move on till this has been mastered, and it does provide a platform. And for many non-native speakere that's quie enough.
The real question, as you pointed out, is what percentage of situations does it cover. I remember reading somewhere that this could be as low as 55% (sorry, can't remember where); so at some stage, as you say, one has to address this reality; and the only way to do it is to make it clear that the 123 approach is an (over?) simplification. That is, without actually saying "well it's all bollocks" ;0))
Just to muddy the waters, I believe French Canadians are perfectly happy to put "will" or "would" in the "if" clause and consider that "correct". This can be very undermining if one is paired with a teacher from Quebec.
I must add that in speaking or writing a foreign language I find the odd mistake with tense is not the issue; being able to come up with the right vocab off the cuff is what really makes a difference to communication.

Once one recognises that the simple 'past' in English includes an unmarked 'unreal' (or subjunctive) meaning, it is easier to go along with just choosing whatever verb form best fits the context (put forward by Michael Lewis in the lexical approach). First, second and third conditionals are to me but an intermediate crutch for non-native speakers. In the above sentences using a (real) present confuses the reader as to whether the situation is unreal or not.

@JJM I do agree that short examples with no context can be very misleading.
This all began when a student asked me when they could use the past participle (or third form) as an adjective, and "withered" came up as an example from the text we were using; so the other examples were made up with verbs where different forms/usages are marked.
To someone using English as a second language it may not be obvious why "a happened situation" is wrong whereas "a withered arm" is okay, when the grammar seems at first glance to be the same.

"I am inclined to think that one's education has been in vain if one fails to learn that most schoolmasters are idiots."
Hesketh Pearson (1887-1964) British biographer.

@WW RSS works from an XML format; I presume that the PITE feed for XML is somehow sent before the database is updated. At the head of the page there is an "About" option which gives contact info. In my experience the guy is quite helpful.

@ww sometimes the system comes up with "your name is being used by someone else", adding the epithet is simply a work-around. Possibly my IP address changes depending on proxy server.

@gallitrot2 Sometimes the system comes up with a message like "name already being used " ; the trick is to add an epithet as a separate word - the post is then accepted. That's why you may see "jayles the unwise" (like ethelred the unredy)

Of far more noteworthiness is the on-going latinization of English; take a look at this:-
http://books.google.com/ngrams/graph?content=unseemly%2Cinappropriate%2Cunbecoming%2Cunbefitting&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=

or try comparing unseemly, unbecoming, and inappropriate on books.google.com/ngrams

Hugh Grant? What's wrong with 'im guv?

"Substantive" is a term widely used in auditing and has nothing to do with substantial

https://en.wikipedia.org/wiki/Audit_substantive_test

It is commonly contrasted with a systems audit, and often focuses on looking at major transactions and items, so ideally all big stuff is audited and just a random sample is taken from minor items and checked.