1. they all require a reader to implement some manner of additional and/or unnecessary mental computation in order to understand the sentence, and

2. the writer of the sentence will never notice the potential pitfalls of such sentences precisely because the writer wrote them, i.e. the writer already knows what the sentence is supposed to mean and so will likely not notice potential ambiguity and will not think to revise such sentences.

An important point to note is that the TFR items do not, in isolation, seem particularly troublesome. However, recall (or view for the first time) the comments about how the TFR relates to the course goal of helping students improve revising skills: the TFR list gives you a starting point to practice revising the sentences you write.

The point of this page is to explain why the list contains the particular items that it does.

As for Simple Sentence Syndrome, the problem is that strings of simple sentences require the reader to do the extra work of figuring out the relationship of the ideas from one sentence to the next. Rather than forcing the reader to read a series of separate claims and infer the logical relations between the ideas in each, writers should do some of the work for their readers and combine simple sentences in order to provide readers with the logical relations between the ideas.