Gloss to noun form.

@@ -31 +31 @@
-<gloss>just for show</gloss>
+<gloss>doing something just for show</gloss>

I am inclined to agree. I can't see evidence of ダテ being used that much.

would it make sense, then, to remove the katakana reading?

I'm not seeing why it is included, and the instances I find on the www lead me to believe the katakana version is only used for stylistic effect (that is, to make the word stand out while avoiding kanji in hiragana-heavy sentences) or possibly because the writers feel their meaning is slangy (plausible for gloss #2); nevertheless, the katakana version is quite a bit more rare than both the kanji and hiragana versions.

@@ -13,4 +13,0 @@
-</r_ele>
-<r_ele>
-<reb>ダテ</reb>
-<re_nokanji/>

as you can see above it is not the primary one.  it appears first on wwwjdic as a result of having both [uk] and [nokanji] tags.  that is ~usually~ a good solution to the problem of biological species (which is where the [nokanji][uk] combo normally appears), as it means that 鴨[かも;カモ[nokanji]] appears as カモ 《鴨》【かも】on wwwjdic.