This rule is triggered when two blockquote blocks are separated by nothing
except for a blank line:

```markdown
> This is a blockquote
> which is immediately followed by

> this blockquote. Unfortunately
> In some parsers, these are treated as the same blockquote.
```

To fix this, ensure that any blockquotes that are right next to each other
have some text in between:

```markdown
> This is a blockquote.

And Jimmy also said:

> This too is a blockquote.
```

Alternatively, if they are supposed to be the same quote, then add the
blockquote symbol at the beginning of the blank line:

```markdown
> This is a blockquote.
>
> This is the same blockquote.
```

Rationale: Some Markdown parsers will treat two blockquotes separated by one
or more blank lines as the same blockquote, while others will treat them as
separate blockquotes.