  Web platforms have allowed political manifestation and debate for decades.
Technology changes have brought new opportunities for expression, and the
availability of longitudinal data of these debates entice new questions
regarding who participates, and who updates their opinion. The aim of this work
is to provide a methodology to measure these phenomena, and to test this
methodology on a specific topic, abortion, as observed on one of the most
popular micro-blogging platforms. To do so, we followed the discussion on
Twitter about abortion in two Spanish-speaking countries from 2015 to 2018. Our
main insights are two fold. On the one hand, people adopted new technologies to
express their stances, particularly colored variations of heart emojis ([green
heart] & [purple heart]) in a way that mirrored physical manifestations on
abortion. On the other hand, even on issues with strong opinions, opinions can
change, and these changes show differences in demographic groups. These
findings imply that debate on the Web embraces new ways of stance adherence,
and that changes of opinion can be measured and characterized.
