As Mario pointed out, giving things up for Lent is by no means specifically Catholic. It isn't even specifically Christian - well, it is for Lent itself, but the idea of having a time of the year like that has been very widespread. Notably with Muslims and Ramadan of course - now that is serious fasting.

The idea is to do without things that aren't bad in themselves, but you flex your muscles by doing without them for a bit, and maybe longer. Giving up on responding to trolls and suchlike fit the bill nicely.