Some other feature sets that we experimented with, via cross-validation on the training set, included word embeddings trained on a generic Twitter corpus (not the domain corpus), the number of occurrences of each part-of-speech tag, the number of repeated sequences of exclamation or question marks, and the number of words with one character repeated more than two times (for example, yessss).
they did not improve results there, and so we did not include them for the test set experiments.