The phrase "felt mildly" is grammatically correct and is commonly used in written English.
Example: After hearing the news, she felt mildly disappointed but tried to remain optimistic.
Back at home in Muswell Hill, Litvinenko felt mildly unwell.
Now alone, Norton looked down and felt mildly pleased that he had barely touched his Martini.
But rather than the triumph of a pioneering moment, it felt mildly embarrassing that the combination should be notable.
The change of setting did not change my luck — within approximately 10 seconds I lost $50 and felt mildly nauseated.
A caveat: the shorts are thigh skimming in the extreme; I felt mildly pornographic walking down the street with no beach in sight.
But that plucked-from-obscurity story line always felt mildly insulting to Ms. McKenna, who'd been a steady presence in the folk music world for years.
"Persecution is not being made to feel mildly uncomfortable.
The BMW's steering is great at filtering unwanted vibrations but feels mildly isolated.
JONATHAN TROPPER understands if you feel mildly disappointed upon meeting him.
It almost comes across as boasting and I feel mildly irritated.
This year's Whitney Biennial, the most poetic I can remember, feels mildly unhappy and restlessly alert.
