The 0.30 spec does not mention that link reference definitions can be interrupted by other elements.
It does say:

However, it can directly follow other block elements, such as headings and thematic breaks, and it need not be followed by a blank line.

and then it gives the example (215):

[foo]: /url
bar
===
[foo]

This is, as the text said, "not followed by a blank line", because the link reference definition has unambiguously ended before the bar. However, there are other cases where a link reference definition could arguably be in progress but the block structure interrupts it.

I suggest adding replacing examples 215-216 with something like:

The text of a link reference definition can be interrupted by any block element that can interrupt a paragraph:

Example A

[foo]: /url '
bar
'

[foo]

Example B

[foo]: /url '
# h1
'

[foo]

Example C

[foo]: /url '
> quote
'

[foo]

Example D

[foo]: /url
'
- list item
'

[foo]

Example E

[foo]: /url '
        not a code block
'

[foo]

Example F (== example 216)

[foo]: /url
===
[foo]

Example G

[foo]: /url 'bar'
===
[foo]

Example H

[foo]: /url
'bar'
===
[foo]

Example I (== example 215)

[foo]: /url
bar
===
[foo]

Example A is a link reference definition with an ordinary multiline title.
Examples B, C, and D do not have valid link titles: the title text is interrupted by block-level structure. Whether the overall link reference definition remains valid depends on whether the title started on a separate line.
Example E is a valid link title: indented code blocks cannot interrupt paragraphs, so they also cannot interrupt link titles.
Examples F, G, and H are valid link reference definitions: they are completed, leaving no paragraph text for the === to use to create a setext heading.
Example I also completes a valid link reference definition, leaving the unquoted bar for use in the setext heading.

Along the same lines, after example 218, I suggest adding something like:

The text of a link reference definition can be continued using the same rules as for paragraph continuation lines:

Example J

> [foo]: /url '
hello
'
> [foo]

This is all a bit roundabout and it would seem easier to say something like "Link reference definitions are removed from the start of each paragraph's initial text as the paragraph is accumulated. If no text remains, then there is no paragraph left behind." But that's probably too operational for the spirit of the spec.