And let the validator speak for me.
Validation Output: 2 Errors
Line 20, Column 6: document type does not allow element “SPAN” here; missing one of “P”, “H1”, “H2”, “H3”, “H4”, “H5”, “H6”, “PRE”, “DIV”, “ADDRESS” start-tag
<span>I’m fine, thank you. My brother though may have some issues.</span>
The mentioned element is not allowed to appear in the context in which you’ve placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you’ve forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as “<p>” or “<table>”) inside an inline element (such as “<a>”, “<span>”, or “<font>”).
Line 22, Column 6: document type does not allow element “SPAN” here; missing one of “P”, “H1”, “H2”, “H3”, “H4”, “H5”, “H6”, “PRE”, “DIV”, “ADDRESS” start-tag
<span>But wait, what about me?</span>
That is invalid and a bad example. You can’t have a span as a direct child of the body as it is invalid.
It would also be non semantic should you wrap it in a div because then it runs into a block level element at the same level which should be avoided (although not invalid - just non semantic because you finish a block element you should start another block box or the browser has to construct an anonymous block to do this. Besides that is a recipe for disaster in iE as it just hates inline elements running ito block elements).
Ignoring all those issues you could of course just set the span to display:block so please no more contrived examples
I said we’d just have to agree to disagree on this point as you have your point of view and I know you won’t change and I accept that.