gg5

Ah, I misread meikyo's entry. If a modern dictionary is listing this as transitive, I don't think there's any issue with doing the same here.

@@ -18 +18 @@
-<pos>&vi;</pos>
+<pos>&vt;</pos>
@@ -20,0 +21 @@
+<gloss>to take pride in</gloss>

of my sources, shinmeikai and meikyo (2nd ed) both list as [vt]; koj and oubunsha kogo jiten both list as [vi].  i can't find it in nikk but kotobank's search sucks pretty bad.

so my refs are split 50:50.  my sense from which refs list it which way is that treating it as [vi] is more old-fashioned/classical and treating it as [vt] is more modern.   i'd be inclined to keep listing it as [vt] based on "helpfulness to learners", as you note

koj, nikk, meikyo

Although 誇る often takes を, the kokugos consider it intransitive (due to a different understanding of transitivity in Japanese).
There's probably a discussion to be had about whether we follow the kokugos in cases like this or just use the English definition of transitive (which is probably more helpful for learners).
But up until now, we've gone with the former approach, so for consistency's sake we should probably put it back to vi.

@@ -18 +18 @@
-<pos>&vt;</pos>
+<pos>&vi;</pos>

@@ -18 +18 @@
-<pos>&vi;</pos>
+<pos>&vt;</pos>