Which emoji are you talking about and which font are you talking about? Specifying your OS is also relevant because different OS have different font file/version for a given font. I do believe you have no idea if the character/glyph/emoji you're talking about is present in the font you're using or not, and because mIRC isn't the only program to do this, it can be tricky to find out if the font has the character or not.

This often leads them to think the font they are using does have the glyph (at least in the mIRC context) because Windows by itself (but mIRC as well when custom drawing), will use fallback fonts to find a character (glyph), this is done to avoid displaying something else than the correct character, whatever that could be.

Non experienced (with fonts/mirc/Windows) users usually have no idea about which or if their font has a given glyph. If you're using a font which has the glyph you are looking for, then it probably works fine under wine, otherwise wine users wouldn't be too happy.

MIRC 7.74 for windows download