Newline undue with a float

In a p (text-align justify), there is a span with a float right 
property. Rendering this, Amaya introduces a newline where the span is. 
The text following the span begins on the next line. The broken line 
gets a queer justification.
This looks like the following where the position of the span in the code 
is given by *

1a.         This           is           some            text.            
[*Newline not asked for]
2a. Here text following span and more and   Floating span begins here
3a. more and still more…

This what I expect:

1b. This is some text. [*No newline] Here text following span and more
2b. and more and still more…                 Floating span begins here

I understand that once a line begins, it is too late to admit a float 
asked after the beginning. Thus the float begins on next line. But I do 
not see a justification why a float should interrupt the normal flow. 
The float should only reduce the width available and non floating text 
should flow continuously in the reduced width.