nornen:Just to avoid that some beginner reads this thread and gets funny ideas:

Vestitor:la pordo estas malfermi = the door is open.

Is this correct?
If it were my job to open something, I would say "Mia devo estas malfermi", but I fail to see the meaning of "La pordo estas malfermi."

You fail to get the meaning of it? That's quite bizarre, since you appear to have parsed it enough to analyse it. It's not about anyone opening a door, it's about a door being open. But okay, is perhaps La porda malfermitas better?

nornen:The fact that the adjective "open" (malferma, offen, abierto) and the verb "open" (malfermi, öffnen, abrir) are the same in English, shouldn't be a reason for haphazardly mixing parts of speech in Esperanto.

I haven't haphazardly mixed anything, unlike the above pot pourri of Esperanto/German/Spanish set in contradistinction to English for some reason. Though German has a minor difference between verb/adjective the basic form is also the same, so it's not me trying easily Anglicise everything.
As I already remarked, Aperti is the later coinage and the less common word.

Vestitor:...is perhaps La porda malfermitas better?

I am no expert but this is how I would say it:
La pordo estas malfermita.
La pordo malfermitas.

Vestitor:It's not about anyone opening a door, it's about a door being open. But okay, is perhaps La porda malfermitas better?

Ordinarily one would render "The door is open" as "La pordo estas malfermita" (there's no particular agency assigned to this, though you might assume that since it is open, it was opened at some point by someone or something). "estas malfermi" doesn't work grammatically, it sounds like "is to open", doesn't really make sense in Esperanto. "La pordo malfermitas" would be a rare choice but technically correct.

The only time I'd expect to see an infinitive with "estas" in Esperanto would be in a sentence like "Mia intenco estas manĝi multe!", something like that.

Vestitor:
You fail to get the meaning of it? That's quite bizarre, since you appear to have parsed it enough to analyse it. It's not about anyone opening a door, it's about a door being open. But okay, is perhaps La porda malfermitas better?...

Vestitor, while I can't speak for Nornen, it seems obvious to me that he was politely trying to point out your mistake without being offensive. Is there a reason why you can't simply say, "oops...you're right; thank you for pointing that out" and let it go at that?

Polaris:

Vestitor:
You fail to get the meaning of it? That's quite bizarre, since you appear to have parsed it enough to analyse it. It's not about anyone opening a door, it's about a door being open. But okay, is perhaps La porda malfermitas better?...

Vestitor, while I can't speak for Nornen, it seems obvious to me that he was politely trying to point out your mistake without being offensive. Is there a reason why you can't simply say, "oops...you're right; thank you for pointing that out" and let it go at that?

Perhaps you were reading a different post, because the one I saw was a point-for-point jab at everything with the (erroneous) added insinuation that I was carrying structures from English over into Esperanto.

I'm not afraid or too proud to be wrong, which is evidenced here if you are willing to look at every post I have made, rather than just the more heated ones.

Vestitor:
Perhaps you were reading a different post, because the one I saw was a point-for-point jab at everything with the (erroneous) added insinuation that I was carrying structures from English over into Esperanto.

I'm not afraid or too proud to be wrong, which is evidenced here if you are willing to look at every post I have made, rather than just the more heated ones.

So what if you WERE carrying over structures from English into your Esperanto? It's not like an attack or an accusation, Vestitor, why take umbrage?

The fact is, you really can't say "la pordo estas malfermi" (and you certainly can't say "la fenestrA estas fermi aux malfermi)", because using the infinitive is creating a predicate nominative construction--you'd essentially be saying "the door is (the act of) opening", which is not what you're trying to say.

But look, even if we don't agree, we're all here to help one another...why be touchy?

It's you who is going on about it, not me.

Polaris:
The fact is, you really can't say "la pordo estas malfermi" (and you certainly can't say "la fenestrA estas fermi aux malfermi)"...?

As Yoda says: "Say he can, just he did. Whether the other understand this will, that another question is."

Another good example that I just thought of is how some religions classify people as believer and non-believer. This is a subtle way of indicating that a non-believer is lacking in some way. It subconsciously indicates that being a believer is supposed to be normal or proper.

Imagine if someone labels you as a non-Christian, as if being a Christian is somehow a standard that people are supposed to be. It seems that most religions do this.

Mal in Esperanto acts the same way by indicating what should be normal. Amo kaj malamo. Dekstra kaj maldekstra.

Alkanadi:Mal in Esperanto acts the same way by indicating what should be normal. Amo kaj malamo. Dekstra kaj maldekstra.

I can see your argument from English, but Esperanto is not English. Mal- in Eo does not indicate abnormality. It just means 'opposite': rekte la kontraŭo, inverse. It doesn't contain any inherrent value judgements, and we shouldn't read them in