Maybe I should withdraw this, but I think my misconstruction of the question was not uncommon, so I will note that, after rereading, I recognize that the actual question concerns a bias towards irregularity in all verbs whose plain forms end in a 'd' sound. (And it appears that the OP even limits the question to the voiced d.)
In which case, he may be sensitive to the doubling of d sounds, as noted by others, but has a workaround rule in '-ed', also noted by others.
(Off the top of my head, just a few more of the short regular verbs ending in the d sound that take the workaround:
add, aid, bead, (bide goes both ways), brood, bud, (chide goes both ways), crowd, crud, confide, deed, (fud is a bit new in coinage), flood, gad, goad, hood, (i-d is a bit new in coinage as a verb), jade, kid, load, lead (as in applying the metal -- not the verb that conjugates to led), (mod is a bit too recent, maybe), (mead and mud might be too technical in context), need, nod, pad, (plead goes both ways), plod, pride, prod, raid, (reed might be too technical), (rid goes both ways), rod, seed, side, (sod goes both ways, I guess), stead, stud, tide, thread, void, wade, weed, wad, wood, ...
Why these are not irregular would be an interesting subject of study, and would help parameterize the suppression.
And I'm falling asleep. 8-)
Surveying all verbs to find all verbs ending in the d sound is going to be a large task unless one happens to have a dictionary of verbs in computer readable form handy.
The reverse task, to list all irregular verbs and examine the etymology of their morphologies for the application of a suppression mechanism might be quicker if such a dictionary is not handy.
It is an availability bias. You can find some lists of irregular verbs in the Oxford English Dictionary and on wikipedia. The verbs in those lists which end with a "d" are in the minority, actually.
(addendum: the list of irregular verbs, borrowed from wikipedia and wiktionary, non-basic forms removed, flagged for final d/t.)
Examples of irregular verbs not ending in "d" include fly, sew, run, begin, think, swim, lie, and so forth.
The conjugations do have patterns, which are discussed to some extent on the wikipedia page, see the discussion of strong vs. weak verbs.
And there seem to be patterns relative to the plain form ending in "d", but I'm not familiar enough with this information to describe them. Country of origin seems to play a large part, but that's not all.