font size different in epub/mobi

I use 18 pt font in the editor. I have this set as the default font size.

Although I’ve already been admonished for using styles, I put a style on everything, because I want dialog to be all-lines indented and narration to be only first-line indented. IOW, not using a style at all makes everything the same, which I do not want. Case closed, I think. If there is a better way, I’m all ears.

But here is the real issue:

If I neglect to add a style to a new line I might insert in a document, say, during a revision, when I compile that project to epub or mobi, the line without a style attached to it displays [size=150]a full three sizes the size[/size] of lines with styles attached. There is no indication or courtesy warning in the editor that I will get this nasty surprise, until I compile—everything appears as 18 pt. in the editor.

So I have to be super-vigilant about making sure everything has a style invoked.

I’d really like a solution to this. One thing I would be happy with is if new lines were of a slightly-larger size in the editor as I add them, because this would at least remind me to add a style to them (which would bring it back down to 18 pt)