>>2567385"><3" is just "<3" in greentext - greentext of course being a type of quotation indicator regularly used on 4chan. You likely know of it, or you've at least probably seen it before. For example:
>this is "greentext">writing <3 at the start looks like...><3 <- this>which is what the commenter saidIn this case, it refers to the "<3" OP wrote at the end of their sentence.
As to why one should stop writing "<3", which is what the commenter seemed to advise OP to do, they may simply disapprove of it because they think that it is an annoying, overused, or silly emoticon, or perhaps they simply shun its use for some other personal reason.
