import re

# ...

i = 0
# unique_reasons -- массив хуёво нарезанных строк
while i < len(unique_reasons) - 1:
    if (re.match(r'[А-ЯЁ]', unique_reasons[i][0]) and
        re.match(r'[А-ЯЁ]', unique_reasons[i+1][0])):
        i += 1
    else:
        unique_reasons[i] = unique_reasons[i] + ", " + unique_reasons[i+1]
        del unique_reasons[i+1]