Fire Yahoo's developers and start over.
The chat functions are simply broken, on all devices. They don't work well at all, and while engaging in a conversation or debate is fun, Yahoo makes it an absolute headache just to stay plugged in. It bounces around from text to text while you're looking for your past text, text often times covers other text, etc. It's ridiculous that a company as large as Yahoo can program their websites right.
Hi there,
I'm sorry to hear you're experiencing this issue and I'd like to look more into it to help, please contact us on Twitter at @YahooCare or on Facebook at our Yahoo Customer Care page. If you do not have a social media account, we are available at help.yahoo.com through the ''Contact us'' link.
Thank you,
Yahoo team