Our forum has also expressed reluctance to change (which is common) and was very averse to reactive emojis other than the heart so that got turned off. I don’t use mobile a lot but I don’t know how it’s possible to “hover” an avatar on mobile to see the name.
I’d prefer clicking the number by the heart and seeing a list of names with small avatars instead of a giant grid of Gravatar colors and letters. Our forum isn’t huge though and rarely do posts get liked more than 10 times, and 20-25 happens but is rare.
It doesn’t need to be tiny to stay out of the way. If someone clicks to see likes they want the info, so a larger modal pop-up temporarily in front of the interface showing avatar/username/name in a scrollable list would be fine (maybe even allowing user to hover names on that list to show the entire user profile card). Usually when viewing likes, people aren’t simultaneously needing to read message content.