Good question again, Chris-san!
It’s a writing technique called 体言止め (ending a sentence with a noun). It’s used to make the writing more compact, to add a different rhythm in the writing or to get the reader’s attention. In my case, if 体言止め is not used:
うちのマンションの入り口のドアはガラスでできています。
ある日、散歩のあと、ごまはガラスのドアが見えなくて思いっきり頭をぶつけました。
それ以来、慎重に確認しています。
All the sentences end with ます form which is repetitive. So I used 体言止め to add a different rhythm. It also implies that another statement about ごま will follow, which can draw the reader’s attention.