I see Blackwall as reformed. Solas is still bad to the bone 
I don't mean he's entirely reformed
What I mean is that he seems to be a textbook example of a dynamic character. He's someone who learned a hard lesson from life and changed himself throughout... even if his journey isn't yet over.
Hence I suspect he might have been much 'wilder' in the past, which eventually contributed to first crisis. He even admits to being "hot-blooded and cocky, always ready to fight" in his youth as well and - like I said earlier - he admits to Varric that 'he's not much of a gambler anymore', which means that there were times when he was way more of a risk-taker.
It might also explain why he has such allergic reaction to Sera - for all the differences between them, there are also pretty significant similarities. I think Solas might not be very fond of her because she may remind him of himself from the past - obviously, I don't think he was ever as ditzy or random, but likely was way more idealistic, spontaneous and fond of taking risks or thought of the world as simpler than it was.
I also wouldn't be surprised if he was popular with the ladies - he's way too smooth and comfortable with flirting for someone who's apparently been so sheltered most of his life. Probably ate young elvhen maiden hearts for breakfast. Might be even that his popularity among the people he led made him even more careless and prideful, which eventually led to his downfall. He seems to admit it when he (almost tearfully
) tells Cole that what he did was "A mistake. One of many made by a much younger elf who was certain he knew everything".