And so finally to LPD. Rather than omit reference in the entries to possible intrusive r like EPD, or use an ad-hoc notational convention like ODP, for LPD I applied a notational convention not restricted to the matter of intrusive r. Namely, LPD divides “optional sounds” into two categories. Those shown in italics are “sounds which the foreign learner is recommended to include (although native speakers sometimes omit them)”. Those shown as raised letters are “sounds which the foreign learner is recommended to ignore (although native speakers sometimes include them)”. Put another way, sounds shown in italics may optionally be elided; those shown raised may optionally be inserted.
Since both categories are optional sounds, what is the basis for distinguishing them? You may well ask. It is covertly orthographic, though not only orthographic. The t segment that some but not all speakers use in mints mɪnts is reflected not only in the spelling but also morphologically, since the t of the singular mint is not a candidate for elision. In mince mɪnts, on the other hand, there is no such support for the plosive used by some but not all speakers.
Here is what LPD says about linking and intrusive r.
Since LPD, unlike the other dictionaries, transcribes in full the inflected forms of monosyllabic verbs, its entries for saw, -ing and soar, -ing are longer, more explicit, and therefore more complicated.
Here is the entry for withdrawal.A word on my own personal usage. I use intrusive r freely after ə, ɑː and the centring diphthongs, even word-internally, but never after ɔː. So I would readily put an r in china and glass, Grandma again and even in semi-nonce forms such as concertinaing, magentaish; but not in thaw out, sawing, withdrawal. Historically, I think this constitutes an intermediate step between an earlier generation (DJ) that still distinguished ɔə (soar) from ɔː (saw), with consistent r links after the first but not after the second, and later generations for whom the two categories are entirely merged as ɔː. You could say that those like me have the phonetic merger of the two categories but not yet the phonological (lexical) merger.
You may think that the theoretical underpinning of the distinction between optional elision and optional insertion is weak. In its defence I would say that it does nicely cater for (i) usage such as my own, consistently distinguishing mints – mince and sawing – soaring, and (ii) statistics such as those furnished by Hannisdal, who showed that in newsreaders’ usage linking r was found significantly more often than intrusive r, even though both categories are frequent.