Ah, right. That sounds great, yes, and very useful 
The choice to have uppercase dialogue would be great, but in actual fact uppercase is going out of style in comics scripting. Mainly for a similar reason as the embolden/underline issue - back in Ye Olde Days, when everything was lettered by hand, it didn’t matter if your dialogue was typed out in uppercase, lower case, sentence case or whatever.
Now that 99% of lettering is done on a computer, however, it’s a different matter. The letterer will copy and paste your scripted dialogue right onto the page, which is great for accuracy (assuming the writer can spell!) but makes a certain problem, that of the “I” character, a pain in the neck. There are two distinct types of “I” character in comic book lettering, one with crossbars - I - which is used for the pronoun (I, I’m, I’ll, etc.) and one without crossbars - | - which is used everywhere else, because an I with crossbars in the middle of a word has bad kerning and looks horrible.* Digital comic fonts get around this problem by having two separate characters both mapped to the I key - uppercase gives an I, lowercase gives an |.
All of which is a very dull and longwinded way of saying, sentence case (as in, what we use here on the board) saves your letterer from having to go through every dialogue balloon and replace all those uppercase “I” characters… and you should always be nice to your letterer, because they also letter the on-page credits 
*Yes, I’m using the pipe character to show what I mean. Indulge me.
Thanks for the heads up Antony. Good to know. This is one good thing about Final Draft. It upcases my dialogue in the template but a quick change of template and everything is back to lowercase (except anything I intentionally capitalized).
I wish Apple would introduce an “All caps” attribute for fonts (Word lets you do this somehow, I think), kind of like the way you apply bold and italics. That would be ideal for this sort of thing. Sigh.