Why is praying in front of a mirror considered Makrooh? If the concern is that seeing ourselves may seem like imitating prayer to ourselves, does that mean praying in a room with a mirror nearby is not Makrooh?
All Islamic rules of Wajib, Haraam, Mustahab, Makrouh and Jaa'ez are based on our own benefit which is best known by Allah (SWT). We gave no right to argue if we really believe in The Absolute Knowledge, Wisdom and Mercy of Allah.
Praying in front of a mirror is Makriuh. If the mirror is nor in front of us while praying, it will not be Makrouh to pray there. After all, Makrouh is not forbidden but it is always better to avoid it.
Wassalam.