What STYLE is the text formatted as? (what does the style dropdown
show, when the caret is planted in the inserted text?)
Assign a style to the text, see what happens?
Also, try CTRL-Q (revert para to assigned style), select text and try
CTRL-SPACEBAR to remove any text/font overrides.
What font size and face does the text come in as? Is it the same as
"default"?