An address is often (e.g. n letterhead) printed on a single line; the
semantics are that the address has different parts, often called lines
- street address, town or city, region, country, province or state, and
so on - and there is absolutely nothing semantic about a br element
there, it’s just one way of formatting. Use a “line” element or the
appropriate named elements if you want to facilitate further
processing, if you want to capture the meaning, the semantics.
In a header, you might want a responsive line break, so you want to
indicate primary and secondary conditional break points depending on te
space available. HTML and CSS aren’t all that good at this today
unfortunately, but you could use br elements with class attributes
indicating primary or secondary, and use media queries to make the
breaks conditional on the space available.
If you want phrase breaking, and there’s no secondary break concerns,
you could use a span class=“phrase” and control line breaking that way.
You could also use one of the “pre” variants, e.g. pre-wrap, and have a
newline where you want a break.
, by the way, is woefully inadequate for poetry, as you can’t
easily arrange an indent after a br element - you need a line element.
HTML has never really managed to climb to the heights of poetry. There
isn’t much poetry in technical documentation, and there’s no easy way t
right-adjust wrapped lines with a [ separator, sharing the same line
as the next if there’s room, nor any standard way to mark the author of
the poem and to distinguish that from the transcriber. Dublin core, but
no standard place to put it except for cite, which is itself the source
of considerable confusion because of the vagueness of its
specification.
So i think addresses and poetry should be taken as throw-away examples
that were not at all thought out, and certainly not examples of the
deep and meaningful nature of linebreaks 
