If "perfectly splendid" were a proper term to use in such a connection, which it is not, the words themselves would carry all the emphasis possible.

Nothing could really be added to them by any typographical device.

In the same way the common use of profanity among ignorant people probably arises mainly from a feeling that the ordinary words with which they are familiar are colorless and do not express their thoughts with sufficient emphasis.
Just as emphasis in style is difficult when one habitually uses the strongest words and emphasis in voice is difficult when one habitually shouts, so emphasis in print is difficult when one habitually uses large capitals, display type, and italics.

Loud printing is as objectionable as loud talking.
USE OF FULL CAPITALS General uses: 1.

Use a capital letter to begin every sentence and every word or group of words punctuated as a sentence.
_Welcome! We are glad to see you._ This rule does not apply to literal reproductions of matter not originally conforming to it.
2.