The line artifacts are a difficult disappointment with some types of mIRC art containing unicode block characters.
In many clients, the rows of text are 16 characters tall, but the font only renders 15 pixels of block text, leaving a blank pixel separating lines.
In mIRC, that blank pixel is rendered at the bottom of text lines. In some other clients, that blank pixel is rendered at the top of text lines.
For these types of artworks that utilize both foreground and background colors to creatively mask the underline or overline artifact, they will only render 'beautifully' in one set of clients (ie: mIRC) but not others (ie: Irssi, Weechat, IRCCloud) without modifying the art to address those artifacts between clients.
It's just one of those things.
