Any new craze on social media grabs my attention. This week was no different. I began to notice friends' Twitter names appearing with three brackets around them. Once I'd seen it a couple of times I was intrigued enough to investigate.

It turns out the phenomenon has begun to spread as an act of defiance against online Anti-Semitism. The past couple of weeks have seen people adding the brackets to their names in an act of defiance because for the last couple of years the signal has been used by far-right groups to identify Jewish people online.

There's a good explanation of the origins of the brackets here, and as ever when one comes across bigotry and racism online it's a pretty depressing read. What started as a niche white nationalist fad began to be used to attack Jewish journalists and other prominent figures online. Their names were surrounded by three brackets as a kind of code between racists so that they could be identified as Jewish without using the actual words.

As one Jewish writer put it, it's a form of intimidation and threatening behaviour.

In a counter move, Jewish people have begun to reclaim the signal. High profile Jewish tweeters began adding the brackets to their names in a bid to draw attention to the racists' activities.

This has caught on and non-Jewish tweeters have also started to add the brackets to their names. Because it's hard to search for users who've done this it's impossible to know how many have adopted the meme, but just looking at my timeline it's easy to see there are many who have. Google has now removed a Chrome app which automatically added the brackets to people's names when they appeared in articles online if they had a surname of Jewish origin – a small victory for the counter campaign.

As with any trending meme, once I'd found out about it and realised it was an act of defiance against racists, I was tempted to join in. Yet something stopped me. I decided against adding the brackets to my name because it felt a bit too much like virtue signaling – the phenomenon where people behave in the 'right way' online, without actually doing anything in their actual lives to fight injustice.

I'm not Jewish and have never been the victim of online abuse. Of course, I could have added the brackets as an act of solidarity, but I felt like my motives were too mixed. I was looking to be seen as doing the right thing – in effect to be 'cool.' In the end, while admiring the Jewish tweeters who'd appropriated the meme, I didn't join them.

This is in contrast to a similar phenomenon a few years ago when the full horror of the ISIS rampage through parts of Syria and Iraq was becoming clear. They were painting the Arabic letter N on the houses of Christians to mark out those who needed to pay a special tax or face punishment – even death. In the wake of this horrible news many of us added the N sign to our social media.

I was among them – and retain the symbol on my Twitter picture to this day. This felt less like virtue signaling and more like solidarity, primarily because I'm a Christian. I share the beliefs of those being persecuted in the Middle East so it felt appropriate to join in the meme. I was appropriating the symbol in solidarity – and in a tiny way defying the death march of ISIS.

Let's be clear – online memes aren't going to change the world. At best, they're a way to defy the racists and to show solidarity. But what if we took the idea over into our offline lives?

What if German citizens had, en masse, begun wearing the Star Of David in solidarity with Jews being persecuted by the Nazis? Would it have prevented the march towards the Holocaust? Probably not. But it would have been an act of solidarity that went well beyond virtue signaling – it would have cost those who participated dearly.

This idea of cost gets to the bottom of why I feel uncomfortable with adopting the brackets myself. I and my family haven't suffered the horrendous persecution that has been the lot of Jews throughout history. If I haven't born the cost then I should think carefully before participating in the latest social media trend. So I won't add the brackets, but offer a full commendation to Jewish friends who do – keep fighting back against the bigots.

Follow Andy Walton on Twitter at @waltonandy