Issue Summary

When you change the style of a specific text to Preformatted, the new style is applied to the whole paragraph.

This is reproducible on Data Center: yes

Steps to Reproduce

1. Create a new Confluence page
2. Add some text paragraphs 
3. Select a portion of the text, in any of the paragraphs
4. In the editor bar, on the style menu, switch from "Paragraph" to "Preformatted" 

Expected Results

Only the selected text will be converted to monospaced/prefromatted style. 

Actual Results

The whole paragraph is converted to monospaced/prefromatted style.

Workaround

The only workaround possible for preventing this behaviour is to use Confluence Wiki Markup and surround the text you want to convert to Preformatted with {{ and }} brackets