More comments (from others or dummy accounts), linking to it from other threads
There are many indexing services also offer trial for free .
If your comments are 50-100 you can submit in this kind of services and they will be index very next day
Try to sharing the url of the website where your backlink resides on a social media site or make a dummy account and '+1' it.Hi, I'm having trouble indexing some forum comments once they're accepted. Any tips for this please? I was thinking social signals? Thanks.