[Sharparam]

Not sure about the later parts, but the first part can be made more readable/easier to maintain:

local supportedTypes = {
    item = true,
    spell = true,
    achievement = true,
    enchant = true,
    quest = true,
    talent = true,
    unit = true,
    glyph = true
}
 
local function ChatlinkTooltips_ShowTip(self, linkData)
    local LinkType = string.split(":", linkData)
    if supportedTypes[LinkType] then
        GameTooltip:SetOwner(self, "ANCHOR_CURSOR")
        GameTooltip:SetHyperlink(linkData)
        GameTooltip:Show()
    end
end