Mail merge field is inserted with incorrectly placed and inverted first bracket '{' when the paragraph is RTL.

Workaround: Update the field and then toggle it back to code display mode.

Steps to reproduce: 
- Write something in RTL paragraph.
- Insert mail merge field.
Expected: The field is inserted with its normal form: { MERGEFIELD PropertyName }
Actual: The brackets of the field are incorrectly placed: } <some-RTL-text> MERGEFIELD PropertyName }