Present tense: "just now" vs "habitually"

[Thrissel]

I'll have to tr*nsl*t* here something from a book named English or Czenglish? How to avoid Czechisms in English to explain why I said

I've no doubt a native English speaker would understand me if I said "He said he doesn't like it" - but I'd like to know that I should say "He said he didn't like it" instead.

FWIW, it was written in 1989 by Don Sparling, an Englisman who, if I remember correctly, was teaching English at the Brno University in the 80s and 90s.

Reported speech

[...] You'll learn from grammars and textbooks that the form of the verb in the subordinate clause stays the same, when the fact hasn't changed yet:
Galileo showed that the earth goes round the sun.
However, this is not entirely true. Just as natural and at least as usual is the sentence
Galileo showed that the earth went round the sun.
There is a distinctive tendency, especially in spoken English, to consistently keep to the rules of reported speech:
I'm only 18. - She told me that she was only 18.
My name's Doreen. - What did you say your name was?

And I kinda forgot over the fifteen plus years that even in spoken English you still can say He said he doesn't like it when talking about something which hasn't finished yet. My mistake, of course, but I wanted to explain it.

[Níall Beag]

So according to Sparling, the present tense isn't common? Hmm.... not convinced. I'll check a grammar book when I get home.

In 1989, he would probably have been working from intuition, but now we've got massive computerised databases of speech and writing to compare against.

[Thrissel]

In 1989, he would probably have been working from intuition

Huh, it's worse than that, I've done some research and apparently he's a Canadian living here from as far back as 1969.
See here.

ETA: It took me rather aback as the preface to the book expressly says it's primarily dealing with British (as opposed to American) English. Oh my.

[Níall Beag]

Michael Swan's Practical English Usage says:
After past reporting verbs, we usually change the original tenses even if the things the original speaker said are still true.
...
However, it is often also posible to keep the original speaker's tense in these cases.

Longman's Student Grammar of Spoken and Written English is a bit more vague, but seems to agree.

Stick with the past and you'll do alright.