Moderation of user-generated e-commerce content has become crucial due to the large and diverse user base on the platforms. Product reviews and ratings have become an integral part of the shopping experience to build trust among users. Due to the high volume of reviews generated on a vast catalog of products, manual moderation is infeasible, making machine moderation a necessity. In this work, we described our deployed system and models for automated moderation of user-generated content. At the heart of our approach, we outline several rejection reasons for review & rating moderation and explore a unified BERT model to moderate them. We convey the importance of product vertical embeddings for the relevancy of the review for a given product and highlight the advantages of pre-training the BERT models with monolingual data to cope with the domain gap in the absence of huge labelled datasets. We observe a 4.78% F1 increase with less labelled data and a 2.57% increase in F1 score on the review data compared to the publicly available BERT-based models. Our best model In-House-BERT-vertical sends only 5.89% of total reviews to manual moderation and has been deployed in production serving live traffic for millions of users.

Code-switching occurs when more than one language is mixed in a given sentence or a conversation. This phenomenon is more prominent on social media platforms and its adoption is increasing over time. Therefore code-mixed NLP has been extensively studied in the literature. As pre-trained transformer-based architectures are gaining popularity, we observe that real code-mixing data are scarce to pre-train large language models. We present L3Cube-HingCorpus, the first large-scale real Hindi-English code mixed data in a Roman script. It consists of 52.93M sentences and 1.04B tokens, scraped from Twitter. We further present HingBERT, HingMBERT, HingRoBERTa, and HingGPT. The BERT models have been pre-trained on codemixed HingCorpus using masked language modelling objectives. We show the effectiveness of these BERT models on the subsequent downstream tasks like code-mixed sentiment analysis, POS tagging, NER, and LID from the GLUECoS benchmark. The HingGPT is a GPT2 based generative transformer model capable of generating full tweets. Our models show significant improvements over currently available models pre-trained on multiple languages and synthetic code-mixed datasets. We also release L3Cube-HingLID Corpus, the largest code-mixed Hindi-English language identification(LID) dataset and HingBERT-LID, a production-quality LID model to facilitate capturing of more code-mixed data using the process outlined in this work. The dataset and models are available at https://github.com/l3cube-pune/code-mixed-nlp.