Union Flag issue is a real concern for nationalists
Firstly, there is no nationalist majority on Belfast City Council. Due to an electoral anomaly (an effective gerrymander) the nationalist majority votes in the city have not been translated into seats. The motion to curtail the flying of the Union Flag to 15 designated days was proposed by the Alliance Party, a unionist party, albeit a non-sectarian one. Nationalists would prefer to see the tricolour and Union Flag flying side by side to reflect parity of esteem, or just fly a civic flag.
The year-round flying of the Union Jack was an anachronistic assertion of dominance by one community over another. Nationalists and republicans do not seek dominance over their unionist compatriots, only equality.