Is learning coding a must to get placed at ISI Kolkata?

This is a difficult question to answer as your question is not clear whether you’re asking about the ISI entrance exam or the ISI placements. 

Case 1: If you are taking an entrance exam: -

• ISI Entrance Exam will evaluate your depth of knowledge in subjects such as Generalized Mathematics (Basic + Probabilities), Statistics, and so on. 
• The importance of the subjects varies depending on the course for which you are appearing. There will be no need for coding for it. 
• The entrance exam consists of two written papers - Objective: Multiple-choice questions on mathematics; Subjective: Depending on the course you applied for, this paper is divided into several sections.

However, if you are applying for the M. Tech in CSE, you should expect some coding-related questions in both the objective and subjective papers.

Case 2: If you are looking for campus placements within ISI: -

To get a job offer during the placement drive, it is important that you are well-acquainted with coding. It is so because the statistical algorithms are implemented on data using tools/platforms such as R, Python, SAS, MS Azure, and so on. You must be familiar with the coding/implementation aspects of at least one of these tools.