If question is big or has multi part then while responding it is needed to view it.
If the screen space is not big enough to show both then atleast on a scroll questions should be viewable. As of now thats not the case.
Quick question... how can I enable anonymous replies? is it a good practice? and, if it's possible to do so, can I include a captcha to avoid massive spam?
You can enable guest replies in the ACP. I don't think it's possible at the moment to have a captcha but you can enable post backlogging for users of less than 1 reputation and that should catch them and put them in the queue.
Guest replies is a little different than anonymous replies. The point is that only registered users can use anonymous replies. But anyone can Guest reply. I do hope there is an anonymous reply feature in the ACP.