Problem
Right now, Mailspring lets you define a default reply behavior (reply or reply-all), which is then what the button below an email in a conversation will do. If for a specific message, you do not want to do the default action, then you must click the button at the top right of the last email in the chain. This button is great, but only allowing a default behavior at the bottom of the message leads to user mistakes.
Proposed Solution
There should be three bottons visible below a message: Reply / Reply to all / Forward. That way, it is always possible to choose what to do in the moment in an intuitive way. Furthermore, a method should be implemented so that it is easy to switch between these three choices even after starting the draft of the email.
Context
Both of these are the standard in Gmail for example, and I believe, work very well.