Punctuation in titles

I'm going to side with Word on this one... though it pains me to do so. That's a gut-level reaction, without consulting a style guide (bcs they're at work and I'm at home).

And what to do with titles depends on what they are, where you're using them, and the conventions you're supposed to be following.

In the case of "Treasure" I'd leave it without quotes, but no ital.

Hmmm. I'm no expert, but I'd say the second one. I don't think you need a full stop after an exclamation mark.

Personally, I use quotation marks rather than italics, but that's just me. I have no idea if it's right or wrong. It just seems right to me.

Even Word knows that you never need anything more after an exclamation point--if it is being used to punctuate a sentence.

Since you are italicizing the sign's contents, it seems to look wrong. However, I would bet that it is right, because the exclamation point does not belong to the sentence.

If you had enclosed it in quotation marks, to make it clear that the sign said "Treasure!" and that the exclamation point was not punctuating the sentence, but part of the sign, then word might agree that you should use the period. Might depend on Word's settings too. Anyway, I would use quotation marks.