Well, as it generates output like this (linebreaks added):
<p>
<a href="https://covers.openlibrary.org/b/" class="tc-tiddlylink-external" target="_blank" rel="noopener noreferrer"
>https://covers.openlibrary.org/b/</a
>isbn/9780907563150-L.jpg
</p>
I would say that is a fail for any reasonable attempt to use this to display images of book covers. It creates a link to a url which is a proper prefix of the expected one, followed by the remainder of the expected url. Concatenated, they might look the same, but they behave very differently.
I’m assuming that this was a last-minute reformatting, without a subsequent recheck; I’ve certainly been guilty of the same; I do try to avoid it but occasionally forget. Breaking a line into two is often a harmless operation. But if it turns a one-line function, procedure, or macro into two lines, then you need to remember to add the \end.