Is it possible to format text in headings, and whether the suffering from this SEO?

It is believed that the headings h1 / h2 on the page should be only pure text and nothing more, no subfolders , and so on. What is supposedly bad for SEO.
The design is drawn highlighting some of the words in the title color. Is it permissible to use something like:

<h1>Our <i>history</i></h1>

and for tag i in css to register style?
If this is true bad impact on SEO?
June 10th 19 at 15:45
2 answers
June 10th 19 at 15:47
Acceptable, but better span
and than span better? - Delph commented on June 10th 19 at 15:50
June 10th 19 at 15:49
It is believed that the headings h1 / h2 on the page should be only pure text and nothing more, no subfolders , and so on. What is supposedly bad for SEO.

You question should be to the owner of this opinion and the question is, "why?"
Insert anything you want. The robot still chooses from the text there, instead of the structure. So there is that problem of number of characters for the title and that is questionable.

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