List items are fragile in wikitext, and there are many things that can't be effectively embedded in lists. In theory we can just use a `<dl><dd>` tag in wikitext to work around this, but this isn't done in practice, mostly because it looks very ugly.
So instead we have:
```
: This is a comment
: This is still the same comment!
{|
|+ I wanted to embed a table but I had to break out of the list item to do that
|}
: Ok, another item. I'm done with my comment now... ~~~~
```
A better syntax for multiline list items would help. {T114432} interalia proposes a syntax that looks like:
```
: <<< This is a comment
This is still the same comment!
{|
|+ I wanted to embed a table but I had to break out of the list item to do that
|}
Ok, another item. I'm done with my comment now... ~~~~ >>>
```
But there are other alternatives that have been mooted.
One is to use `{* ... *}` / `{: ... :}` syntax, which is based on the [wikitext 2.0 proposal](https://commons.wikimedia.org/w/index.php?title=File%3AWikitext_2.0.wikimedia.devsummit.2017.pdf&page=58). The nested form of that would look something like:
```
:::{: line 1
line 2 :}
```
although different variants are proposed.
Another proposal is to use "traditional" email quoting characters:
```
> line 1
> line 2
>
> * embedded list
```
This doesn't actually conflict with HTML, since `<` is the special character in HTML -- `>` is only a meta character after an initial `<` has been seen. The angle brackets also work well in a RTL context, since they are "logical" punctuation and change direction in a RTL context, for example: https://ar.wikipedia.org/wiki/%D9%85%D8%B3%D8%AA%D8%AE%D8%AF%D9%85:Cscott/AngleTest . However, it is very difficult to cut-and-paste content into a comment, since you need to go through and manually add `>` to each line. In theory you could mix this with heredoc quoting to avoid this, but that results in:
```
>>> Deeply nested reply <<<
multi
line
* embedded list
>>>
>>>> Next item
```
That might be considered bracket overload. By making this syntax only work at start-of-line, we can probably avoid most breakage of legacy content, although probably some folks mask whitespace in wikitext using constructs like:
```
<span class="foo"
>something something...
```
Presumably we'd use entity encoding or `<nowiki/>` to handle quoting content that started with a literal `>` character (this should be rare!), but the [old usenet quoting standard](https://en.wikipedia.org/wiki/Usenet_quoting#Canonical_quoting) considered `>>` and `> >` to be different: the former was a two-level-deep quote, and the latter was a one-level-deep quote starting with a literal angle bracket (the intervening space is removed).
----
It should be considered how well these various proposals account for:
1. Multi-line content
2. Extensions to add attributes to the item: {T230658}
3. Interoperability with existing `:`-style items, since old-school editors will continue to mix "traditional" syntax and new
4. The desire to have an HTML box around "just this one comment". The old-style `:` context technically nests replies in the same box as the original comment, so it is hard to use styles which highlight "just this one comment not its replies".