I think most aren’t taking it too seriously 
I think I use it in a similar way to what you’ve described. I use 
for posts I appreciated reading, and 
for posts I agree with. Not exclusively though, if I liked it and I agreed with it I’d probably just use a or… whatever other people have already used lol
On a technical level they both count as receiving a like (this used to not be the case and only hearts counted) for the purposes of wherever the forum uses like statistics. Like-related badges, trust level calculations, etc. Some reactions do not count as likes.