I kid you not when I say that the Ink Muddler isn’t much bigger than a standard international converter. It is similar in girth (except for the Muddler end, of course). Even the pencil is girthier than the Muddler. If you have larger hands or a lot of swatching to do, the Muddler might be uncomfortable if you don’t like slim and short writing implements.
One of the things I both liked and disliked about the Ink Muddler is that it is two tools in one. I liked it because it meant I had a writing end and a swatching end (or ink mixing end). But I also disliked it because I have to rinse and flip between writing and swatching. I have a multi-step process for swatching (2 Col-o-Ring cards, swatch and writing sample in the Endless Recorder and more recently, in the Hobonichi weeks too). This meant that I had to do all of my writing on different cards/papers, clean the dip nib, flip it around, and then do all the swatching. This would be an improvement over the old days when I used to use a glass dip nib for writing samples and a separate tool (the non-brush end of a cheap paint brush) for the swatching. But now that I’ve switched to the Kakimori in the Kaweco clutch lead holder, I already have a tool that does both.
The other thing about this all-in-one tool is that the dip nib is much more susceptible to getting damaged. This is partly because (1) glass dip nibs are fragile in general (certainly more so than a metal dip nib), (2) being on the same piece of glass as the muddling end means that you have to flip it around to use the other end and therefore, more chances to knock it into things, and (3) the shortness of it means the tip is sticking out when you’re using the muddling end (again, higher likelihood of accidentally hitting something). Or worse, it’s poking you in the hand if you have larger hands.