How can the sender's mail font be preserved?

When an email comes in, a major part of the feeling and tone of that email (and the person who sent it) is its font.  How can incoming email font be preserved, yet reply using my own preferred font?

I had the same issue in Mailbird and also in eM Client: when setting a font, color or template for my mails, the whole mailbody gets formatted that way if it is not specifically enclosed in a formatting tag itself. What I want is to format my text as a means of easily distinguishing my text from the other persons text. What I do not want is to change the formatting of the cited mail. I think this is not what the idea of templates in eM Client is for; it would be a different feature where the formatting intelligently encloses my text only and does not include the other text in the same container.

I contacted the Mailbird support about this but they said it be a feature, not a bug. It depends on what one wants. What I am looking for is sth. like in some chats where you can set format for your own text and your own text only. Is e-mail-HTML able to get this into composing e-mails as well?