Hmm...this one is puzzling. While I agree with JR's interpretation, it prompts me to ask other questions. Here is the relevant wording of C6.5:
C6.5 CASE N; ACQUIRED TARGET: When a Gun (including the MA and SA [Secondary Armament, as per Chapter H Vehicle Listings], of vehicles [EXC: not FT or LATW]) of ≥ 20mm other than a mortar fires at (not Interdicts) a Known unit or a bridge, it may place a 1/2" -1 Acquired counter on its target (or flip over an already present -1 counter to the -2 side), and this Acquired counter then applies as a TH DRM for subsequent shots by that Gun [EXC: Acquisition DRM cannot be used for Deliberate Immobilization attempts; (C5.71); see also C6.54-.57].
The wording leads me to ask, while you can't use an AQ DRM when attempting Deliberate Immobilization (the eponymous "DI", in case I'm not the only only who couldn't figure out what this thread was about!), can you still gain an AQ from a DI attempt? The rule doesn't seem to prohibit the gain!
If not, would you lose an AQ by attempting DI? It's left unsaid, so probably no, but all in all the DI / AQ rule interaction is a little bit wanting in terms of clarity.
Which do we like less?
A) That DI can't make use of an AQ
B) that BS DRM apparently can be used for DI
(...of course there's choice C: "I hate whatever option causes me to lose a game!")