TL;DR: such a change would entail much work for dubious benefits and most
importantly would break backward compatibility.

The problem as I see it is that the possibility of specifying classes *in
two different ways simultaneously* --- one undotted class outside the
braces and any number of dotted classes inside the braces is inconsistent
and thus confusing to most users. People already tend to think that the
lone class undotted class without braces is not just a normal class, which
it is except that the highlighting mechanism picks up the *first* class,
whether undotted and without braces or dotted and inside braces, as the
language name. It might be argued that things could be changed so that a
language name always has to be specified as a/the undotted class outside
the braces, but this is hard to do for several reasons: one is that in
Pandoc's abstract representation of the document this class is not stored
specially; it is just the first in the list of classes, and if it was
"bare" it is *incidentally* the only class. The developers are very
unwilling to change the internal representation (I'm not stating this as
critique but merely as a fact), if I understand correctly because any
change to the internal representation would mean that numerous changes
would need to be made in many places in the code. To users a change would
mean that old documents which rely on the current behavior where the
language class is just the first class however specified would not work
anymore. These two concerns meet when it comes to filters since filters and
the various filter libraries, including but not limited to the official Lua
filter mechanism and its associated libraries, rely on the current internal
representation.

Den sön 30 juni 2019 19:55Chao Xu <mgcclx-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> skrev:

> If it is more intuitive, then it is less confusing.
> When I wrote it for the first time, Theorem {#id} did not work, and that
> was fairly confusing to me...
>
> Also, this update can be helpful towards adding an attribute to all
> markdown elements.
> https://github.com/jgm/pandoc/issues/684
>
> Best,
> Chao Xu
>
>
> On Fri, Jun 28, 2019 at 1:55 AM mb21 <mauro.bieg-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>> I agree that the proposed variant looks nicer. However, it adds yet
>> another way to do the same thing, which may lead to confusion (and may make
>> learning pandoc markdown harder). Another question is whether fenced code
>> blocks would then have to support that style as well...
>>
>>
>> On Wednesday, June 26, 2019 at 5:55:27 PM UTC+2, Chao Xu wrote:
>>>
>>> Does it make sense to make them mutually exclusive?
>>>
>>> The syntax is identical to the `header_attributes` extension. Except for
>>> that string in front is the class name instead of the header.
>>> However, it still makes sense, because often the class name itself acts
>>> as a header for a div.  (warning, theorem, remark, etc)
>>>
>>> I'm suggesting making an enhancement, allowing the one I showed in the
>>> email.
>>>
>>> Best,
>>> Chao Xu
>>>
>>>
>>> On Wed, Jun 26, 2019 at 9:16 AM BP Jonsson <bpjo...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>>>
>>>> The two styles, a *single* class without braces or CSS-like attributes
>>>> in braces, are mutually exclusive, i.e. you can use one or the other on any
>>>> given block but you can't mix them on the same block, so if you want both a
>>>> class and an id you must use {#id .class}
>>>>
>>>> Den tis 25 juni 2019 23:12Chao Xu <mgc...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> skrev:
>>>>
>>>>> Hi all,
>>>>>
>>>>> What should be the desired behavior for the following code in Pandoc
>>>>> Markdown?
>>>>>
>>>>> ::: Theorem {#id}
>>>>> This is a theorem.
>>>>> :::
>>>>>
>>>>> Knowing both::: Theorem and ::: {.Theorem #id} exists, I would expect
>>>>> it behaves as
>>>>>
>>>>> ::: {.Theorem #id}
>>>>> This is a theorem.
>>>>> :::
>>>>>
>>>>> But that is not true. The HTML output is.
>>>>>
>>>>> <p>::: Theorem {#id} This is a theorem. :::</p>
>>>>>
>>>>>
>>>>> Of course, as the current pandoc markdown states:
>>>>> > As with fenced code blocks, one can use either attributes in curly
>>>>> braces or a single unbraced word, which will be treated as a class name.
>>>>>
>>>>> But I do believe what I suggest is more reasonable, especially most of
>>>>> the time there are no additional attributes except the class name.
>>>>>
>>>>> I've raised the issue here.
>>>>> https://github.com/jgm/pandoc/issues/5611
>>>>>
>>>>> Best,
>>>>> Chao Xu
>>>>>
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