In general a DM has a very limited view of the world, and they tend to be busy with setting up things… and occasionally the spam on party channel is too much.
So to ensure you get a response from the DM, please do the following:

If you wish to examine something, the best way is to say in either party or in talk the thing you wish to do:
/p *searching the bandit body for any odd tattoos*

Then follow it by same thing on dm channel
/dm searching the bandit body for any odd tattoos

Then wait a while before saying you found nothing, as the DM occasionally gets quite many requests. Also giving any extra information you wish the DM to remember about your char at that point might help your case. For example a dwarf might say:
/tk *looking at the cave walls and roof for signs of toolmarks*
/dm “Having lived most of my life in caves, does this cave look natural or artificial?”

There are situations when a specific PC is the right person to talk to a NPC. Like talking to a guild, a high-ranking guildmember is much more likely to get a friendly reception, or while talking to orcs a Crog follower is more likely to be positively greeted than a Belwar follower.
And in general someone with high a Charisma score or a good Persuasion skill is often a good choice to speak to people

If you want to cast a spell to cause a DM directed effect you have to inform the DM beforehand, so he has time to set up the effect. The procedure to cast a spell so that the DM will react is:

/dm Preparing to cast mordenkainens disjunction on portal
/tk I think I will cast that Mordenkainens disjunction on the portal
(pause)
/dm casting mordenkainens disjunction on portal
/tk *casting Mordenkainens disjunction on the portal*
(pause)
Do the casting
(pause)
if nothing seems to have happened examine

That way the DM will have time to set up the reaction.