Is it possible to insert tags in the H1 heading tag?

Question

HTML

Greetings
Let's imagine two article titles in a spherical vacuum:

<h1>Заголовок номер один</h1>
<h1>Заголовок номер <span></span> один</h1>

There are a couple of questions:

1. Is it semantically semantically to insert a tag into the title?
   
2. theoretically, how will PSs react to a header with a tag inside, will their algorithms break such a header into parts, or will there be no difference in fact for them? Or is something still going to happen?
   

Answer 1

1. The span element has no semantic meaning. He is neutral. So the code is semantic.
2. PS smart, see point 1.