sudanglo:

in English those two mean the same thing thanks to the simple past being ambiguous

Not really Ceiger.

Did you see Susan (I have a specific occasion in the past in mind)

Have you seen Susan (before now, with no temporal reference).

Note: 'I have seen Susan yesterday' not possible in English.

Yeah but you've added context and further criteria there. Otherwise "Did you see Susan?" and "Have you seen Susan?" wouldn't be any different. You could ask someone "Have you seen Susan?" and get a reply of "I saw here sitting on that bench over there".

Because "did you see" has no real value on the perfect/imperfect scale that say French's imperfect has... At least that's what I thought you were alluding to, because that's the most important past tense distinction I can think of, but it seems I was overthinking Anyway, it seems that Esperanto's past tense actually very nicely matches English's simple past tense, since both are sort of neutral as far as the imperfect/perfect goes.

Anyway, that confusion aside, how does one do a perfect tense construction in EO? Mi estas manĝinta? And pluperfect being "mi estis manĝinta"? I seem to have forgotten, if that's any indication about how little it's used
(Off topic, but I recall reading somewhere that most tense markers in western Indo-European languages tend to stem from consonant doubling, thus evolving into things like re-, -ed, ge-, etc)

You could ask someone "Have you seen Susan?" and get a reply of "I saw here sitting on that bench over there".

Of course you can say that, Ceiger, and the reason is that the questioner is not thinking of a specific occcasion and the respondent has the past event in mind.

Whatever theory you like to advance, it must explain why you cannot say 'I have seen Susan yesterday.

Quite true, I think, that sometimes English will use a simple past when in perhaps another language you might be forced to use an imperfect form. Though I can't think of a good example just at the moment.

However English commonly uses was X-ing or, used to X, or would X to convey the notion of extended action. So the distinction between a momentary action, or action viewed as a whole, and one that was going on is very much alive and well in English.

The perfect notion is probably most often expressed in Esperanto with a participle adverb (X-inte), but the compound tenses (with estas and estis) are not that uncommon in the literature - and necessary often.

Estis varma aŭtuna posttagmezo, kaj forta pluvo estis falinta.

The above sentence would have quite another meaning if you replaced estis falinta with falis.

sudanglo:The above sentence would have quite another meaning if you replaced estis falinta with falis.

Good point. (At least when they are contrasted (perhaps in the same paragraph or whatnot)) You get the impression that the rain suddenly came down at the same time as the time the narration is set in... Nice example!

I don't get the impression that the rain had fallen suddenly.

Rather, "forta pluvo estis falinta" gives me the idea that there had been a heavy rain, but that it had now stopped raining (however we assume that although it has stopped raining, everything is still wet and there is still the smell of rain in the air!)

Sorry, "suddenly" shouldn't have been kept in there.